115-634: The Oxley Wild Rivers National Park is a protected national park that is located in the Northern Tablelands region of New South Wales , Australia in the Port Macquarie-Hastings City Council and Walcha Shire councils. The 145,223-hectare (358,850-acre) park is situated 445 kilometres (277 mi) north of Sydney and is named in memory of the Australian explorer John Oxley , who passed through
230-526: A land lease from the U.S. government , while Mackinac National Park was handed down to become the first of the Michigan state parks . As with national parks, facilities at state parks are often leased to concessionaires to operate. Breaks Interstate Park is operated under an interstate compact by Virginia state parks , although it is also one of the Kentucky state parks , straddling both sides of
345-508: A thundercloud moves over the surface of the Earth, an equal electric charge , but of opposite polarity, is induced on the Earth's surface underneath the cloud. The induced positive surface charge, when measured against a fixed point, will be small as the thundercloud approaches, increasing as the center of the storm arrives and dropping as the thundercloud passes. The referential value of the induced surface charge could be roughly represented as
460-553: A 300 degree view almost from Point Lookout in New England National Park near Dorrigo back to Mummel Gulf National Park near Walcha. On a clear day you can see Mount Duval near Armidale, more than 70 kilometres (43 mi) away. A 4WD vehicle is needed to access Marys View, from outside the national park, and it is at least a seven–hour return trip from either Walcha or Armidale and onto the Carrai tableland. There
575-463: A 4WD is required along with a permit. This historic homestead built in the 1890s, of solid cedar throughout, was once the centre of a grazing empire. It has now been carefully restored by the National Parks and Wildlife Service to provide comfortable and modern accommodation. Edward Fitzgerald's grave is uphill from the rear of the homestead near a clump of gum trees along the fence line. Edward
690-461: A base and carbon dioxide is an acidic gas, it is possible that charged water clouds in which the negative charge is in the form of the aqueous hydroxide ion, interact with atmospheric carbon dioxide to form aqueous carbonate ions and aqueous hydrogen carbonate ions. The typical cloud-to-ground lightning flash culminates in the formation of an electrically conducting plasma channel through the air in excess of 5 km (3.1 mi) tall, from within
805-523: A bell curve. The oppositely charged regions create an electric field within the air between them. This electric field varies in relation to the strength of the surface charge on the base of the thundercloud – the greater the accumulated charge, the higher the electrical field. The best-studied and understood form of lightning is cloud to ground (CG) lightning. Although more common, intra-cloud (IC) and cloud-to-cloud (CC) flashes are very difficult to study given there are no "physical" points to monitor inside
920-459: A bidirectional leader initiates between the main negative and lower positive charge regions in a thundercloud. The weaker positive charge region is filled quickly by the negative leader which then propagates toward the inductively-charged ground. The positively and negatively charged leaders proceed in opposite directions, positive upwards within the cloud and negative towards the earth. Both ionic channels proceed, in their respective directions, in
1035-545: A brilliant, blue-white color. Once the electric current stops flowing, the channel cools and dissipates over tens or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to expand explosively, producing a powerful shock wave which is heard as thunder . High-speed videos (examined frame-by-frame) show that most negative CG lightning flashes are made up of 3 or 4 individual strokes, though there may be as many as 30. Each re-strike
1150-421: A charge opposite of that of the leader tip. The negative end of the bidirectional leader fills a positive charge region, also called a well, inside the cloud while the positive end fills a negative charge well. Leaders often split, forming branches in a tree-like pattern. In addition, negative and some positive leaders travel in a discontinuous fashion, in a process called "stepping". The resulting jerky movement of
1265-404: A combination of methods, including baiting , aerial shooting and cooperative fencing with neighbours. Feral pigs have a large impact on the park and cause ground disturbance that encourages soil erosion and weed invasion. Pigs are trapped, poisoned and are also controlled with ground and aerial shooting. Feral goats are confined to the upper Chandler, Styx, Oaky, and Apsley rivers. They compete with
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#17327730449241380-410: A conductive portion of the main leader network, a return stroke-like process occurs and a dart leader travels across all or a portion of the length of the original leader. The dart leaders making connections with the ground are what cause a majority of subsequent return strokes. Each successive stroke is preceded by intermediate dart leader strokes that have a faster rise time but lower amplitude than
1495-440: A converging point for moister eastern coastal and dry western floras, and some 950 native plant species have been identified, of which 36 are rare or threatened. The rare plants found include: Grevillea obtusiflora , Acacia blakei (subsp. diphylla ) (Wollomombi or gorge wattle) and Acacia ingramii which grows at Dangars Gorge. Some Australian red cedar trees may also be seen in the more remote locations. Threatened flora of
1610-589: A few exceptions such as Anza-Borrego Desert State Park in California, and Wood-Tikchik State Park in Alaska, the largest state park in the United States . In addition to preserving natural landscapes and providing recreational opportunities, many state parks also serve as important educational resources . They often offer guided tours, interpretive programs, and exhibits that help visitors learn about
1725-577: A few local council run recreation areas at sites such as Wollomombi Falls , Dangars and Apsley Falls . With future land-use undecided, the NSW Electricity Commission began surveying the Apsley Valley for a hydro-electric scheme in the late 1970s. The Apsley Gorge National Park of 6,718 hectares (16,600 acres) was gazetted followed by the 3,456-hectare (8,540-acre) Yarrowitch Gorge National Park soon after. During late 1981
1840-482: A great distance but not heard; dry lightning , which can cause forest fires ; and ball lightning , which is rarely observed scientifically. Humans have deified lightning for millennia. Idiomatic expressions derived from lightning, such as the English expression "bolt from the blue", are common across languages. At all times people have been fascinated by the sight and difference of lightning. The fear of lightning
1955-446: A high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges. The atmosphere provides the electrical insulation, or barrier, that prevents free equalization between charged regions of opposite polarity. It is well understood that during a thunderstorm there is charge separation and aggregation in certain regions of the cloud; however, the exact processes by which this occurs are not fully understood. As
2070-637: A locked gate key and permit are essential to use this trail with a vehicle. The Riverside Trail was opened in April 1997 to permit vehicle access to the Macleay Gorges area. The road down to the river shows the diversity of flora as you drop in elevation and visitors can experience groves of native hibiscus ( Hibiscus heterophyllus ) and get to see river bank terraces shaded with large, fuzzy box ( Eucalyptus conica ). Bluff Rock (or The Terrace) walk - 1.5-kilometre (0.93 mi), one hour, medium difficulty,
2185-412: A negative charge. Updrafts within a storm cloud separate the lighter ice crystals from the heavier graupel, causing the top region of the cloud to accumulate a positive space charge while the lower level accumulates a negative space charge. Because the concentrated charge within the cloud must exceed the insulating properties of air, and this increases proportionally to the distance between the cloud and
2300-601: A number of much shorter flashes (strokes) of around 60 to 70 microseconds . Many factors affect the frequency, distribution, strength and physical properties of a typical lightning flash in a particular region of the world. These factors include ground elevation, latitude , prevailing wind currents, relative humidity , and proximity to warm and cold bodies of water. To a certain degree, the proportions of intra-cloud, cloud-to-cloud, and cloud-to-ground lightning may also vary by season in middle latitudes . Because human beings are terrestrial and most of their possessions are on
2415-466: A number of successive spurts. Each leader "pools" ions at the leading tips, shooting out one or more new leaders, momentarily pooling again to concentrate charged ions, then shooting out another leader. The negative leader continues to propagate and split as it heads downward, often speeding up as it gets closer to the Earth's surface. About 90% of ionic channel lengths between "pools" are approximately 45 m (148 ft) in length. The establishment of
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#17327730449242530-535: A permit and key are required. Riverside and Youdales Hut require a low range 4WD vehicle and trailers are not permitted. The Riverside Rest Area is on the banks of the Apsley River, 50 kilometres (31 mi) east of Walcha and is reached by the Moona Plains Road. The trail from Budds Mare Rest Area is a steep gravel track and a 4WD with low range is necessary. Trailers are not permitted. Fees apply,
2645-699: A restaurant) for lodging at some parks. These typically use "Resort" in the name, such as "_____ Resort State Park" in West Virginia state parks and "_____ State Resort Park" in neighboring Kentucky state parks , which has 17 such resort parks, the most of any state. Other states use the Resort name inconsistently (like DeGray Lake Resort State Park , the only one out of three resorts in Arkansas state parks ), or have only one such park ( South Carolina state parks ' Hickory Knob State Resort Park ), or do not use
2760-441: A small sandy beach near the lower exit. A climb down a small waterfall and a curving squeeze can be difficult for some to negotiate. The exits downstream can be difficult to find from the outside. The most significant introduced species are giant Parramatta grass ( Sporobolus fertilis ), lantana ( Lantana camara ), prickly pear ( Opuntia ), blue heliotrope and blackberry . Lantana was widely distributed in warmer lower areas of
2875-622: A state to preserve a location on account of its natural beauty, historic interest, or recreational potential. There are state parks under the administration of the government of each U.S. state , some of the Mexican states , and in Brazil . The term is also used in the Australian states of Victoria and New South Wales . The equivalent term used in Canada, Argentina, South Africa, and Belgium,
2990-451: A threshold and form upward streamers. Once a downward leader connects to an available upward leader, a process referred to as attachment, a low-resistance path is formed and discharge may occur. Photographs have been taken in which unattached streamers are clearly visible. The unattached downward leaders are also visible in branched lightning, none of which are connected to the earth, although it may appear they are. High-speed videos can show
3105-413: Is provincial park . Similar systems of local government maintained parks exist in other countries, but the terminology varies. State parks are thus similar to national parks , but under state rather than federal administration. Similarly, local government entities below state level may maintain parks, e.g., regional parks or county parks . In general, state parks are smaller than national parks, with
3220-493: Is 44 kilometres (27 mi) east of Walcha via the Moona Plains Road. The route includes 8 kilometres (5.0 mi) of unpaved roads, which is unsuitable for standard 2WD cars, because of washouts. Budds Mare is set in bushland and a short walk takes you to the lookout which has extensive views over Gondwana dry rainforest in the Apsley River Gorge. Across the first gorge is the obvious feature of Paradise Rocks and to
3335-563: Is accessible via the historic gold mining town of Hillgrove from the Waterfall Way, 32 kilometres (20 mi) east of Armidale to the Hillgrove turnoff. Head south from Hillgrove for 17 kilometres (11 mi) along the gravel road. Located in a small forest clearing, this campground gives ready access to the easy 1.5-kilometre (0.93 mi) Cassinia Walk; the medium difficulty 6-kilometre (3.7 mi) Chandler View Circuit Walk; and
3450-659: Is also home to the Macleay River tortoise, a recently discovered species, and a rare mammal, the Hastings River mouse ( Pseudomys oralis ), which is considered to be in imminent danger of extinction. Car access to the park is mainly via the Waterfall Way , east of Armidale and Oxley Highway , east of Walcha. All roads to visitor facilities are suitable for conventional cars except the 4WD tracks to Riverside, Youdales Hut and East Kunderang. A permit and key
3565-487: Is an atmospheric electrical phenomenon and contributes to the global atmospheric electrical circuit . The three main kinds of lightning are distinguished by where they occur: either inside a single thundercloud (intra-cloud), between two clouds (cloud-to-cloud), or between a cloud and the ground (cloud-to-ground), in which case it is referred to as a lightning strike . Many other observational variants are recognized, including " heat lightning ", which can be seen from
Oxley Wild Rivers National Park - Misplaced Pages Continue
3680-415: Is an endangered species of shrub that is found in two locations, growing among rocks or in thin soils close to cliff-edges in dry woodland with she-oaks, wattles and tea-trees. The park is rich in fauna, with over 350 species recorded, including 55 mammals . Oxley Wild Rivers National Park is a major refuge for the brush-tailed rock-wallaby ( Petrogale pencillata ), with the largest confirmed population in
3795-434: Is an excellent introduction to gorge bushwalking, and can be undertaken in one strenuous or two leisurely days. From Dangars carpark cross the river (if the river is high do not attempt to cross), and follow the track past the turn off to McDirtys, heading out along the ridge as sign-posted to Sarum Hill Lookout (10.7 kilometres return), descending 500 metres to Salisbury Waters (14 kilometres return). The Long Point campground
3910-580: Is an historic pioneering timber slab walled hut that was built in the 1930s on a small pastoral run established in the Kunderang Gorges. Alan Youdale is believed to have been guided here by an Aboriginal man, and he then settled here in circa 1939. This camping ground is approximately 96 kilometres (60 mi) from Walcha and can be accessed via Kangaroo Flat Road, which leaves the Oxley Highway 55 kilometres (34 mi) from Walcha. The trail
4025-568: Is called astraphobia . The first known photograph of lightning is from 1847, by Thomas Martin Easterly . The first surviving photograph is from 1882, by William Nicholson Jennings , a photographer who spent half his life capturing pictures of lightning and proving its diversity. There is growing evidence that lightning activity is increased by particulate emissions (a form of air pollution). However, lightning may also improve air quality and clean greenhouse gases such as methane from
4140-560: Is located 18 kilometres (11 mi) south-east of Armidale along the Castledoyle Road off the Waterfall Way just east of Armidale. The remains of Australia's first public hydro-electric scheme can be viewed here. Gara Gorge is a picnic area with tables, drinking water, toilets and gas barbecues. Known for scenic bush strolls and the Blue Hole which is commonly used for swimming. The 5-kilometre (3.1 mi) Threlfall Walk follows
4255-531: Is located off Raspberry Road, east of Armidale. The very steep 4WD trail, suitable only for vehicles with a low range, continues on down to a good camping area on the Chandler River. The new facility consists of thirteen camping sites with pit fires, tables, barbecues and toilets. There are several mines in this area and the Halls Peak Mine may be seen from near the camping area. The Youdales Hut
4370-547: Is narrow and steep and a 4WD with low range is necessary. Trailers are not permitted. Access is also possible via Carrai Road, Coachwood Road and the Racecourse Trail from Kempsey, or the Hastings Forest Way and Racecourse Trail from Port Macquarie. Visitor numbers are limited so bookings are essential. A permit and key is necessary to gain entry to this area and they may be obtained from Apsley Motors or
4485-477: Is no vehicle access from East Kunderang. The Bicentennial National Trail for walking and horse riding passes from Cedar Creek on the edge of Werrikimbe National Park past Youdales Hut via East Kunderang to Georges Junction on the Armidale to Kempsey road, which is a distance of some 75 kilometres (47 mi) through the national park. The track is mostly unmarked but follows Kunderang Brook as it descends into
4600-399: Is reached by heading north-west from the visitor area, across a gully and up the hill to the management trail which leads to the top of the bluff rock, overlooking the river and across to Paradise Rocks. Activities: swimming, hiking, fishing and photography. Facilities: 13 camp sites, toilets, picnic tables, electric/gas barbecues, wood barbecues, firewood supplied. The Halls Peak camping area
4715-559: Is required to gain vehicle access to these three sites. There are several visitor entry points where visitors may enter with a 2WD car and camp overnight: The Apsley Falls are located 20 kilometres (12 mi) east of Walcha, 1 kilometre (0.62 mi) off the Oxley Highway. Here the Northern Tablelands plateau drops precipitously into the rugged gorges carved out by the Aspley and upper Macleay Rivers which meander through
Oxley Wild Rivers National Park - Misplaced Pages Continue
4830-418: Is separated by a relatively large amount of time, typically 40 to 50 milliseconds, as other charged regions in the cloud are discharged in subsequent strokes. Re-strikes often cause a noticeable " strobe light " effect. To understand why multiple return strokes utilize the same lightning channel, one needs to understand the behavior of positive leaders, which a typical ground flash effectively becomes following
4945-1073: Is shelter from wind and sun. The adaptable bird's nest fern ( Asplenium australasicum ) grows in a variety of sites as an epiphyte on large trees, independently growing on the forest floor or attached to rocks. Other plants that could be found in or around dry rainforests include: native rosella ( Hibiscus heterophyllus ), gorge mock-olive ( Notelaea microcarpa ), Brachychiton discolor (lacebark), Moreton Bay fig ( Ficus macrophylla ), native olive ( Olea paniculata ), red kamala ( Mallotus philippensis ), scentless rosewood ( Synoum glandulosum ) and shatterwood ( Backhousia sciadophora ). The open forest and woodlands are dominated by various trees. The main species are: Angophora floribunda (rough-barked apple), Eucalyptus retinens (Hillgrove box), Eucalyptus andrewsii (New England blackbutt), Eucalyptus caliginosa (broadleaved New England stringybark), Eucalyptus laevopinea (silvertop stringybark), Eucalyptus melliodora (yellow box) and wild cherry. Eucalyptus tereticornis (forest red gum) identified by
5060-477: Is strongest on grounded objects whose tops are closest to the base of the thundercloud, such as trees and tall buildings. If the electric field is strong enough, a positively charged ionic channel, called a positive or upward streamer , can develop from these points. This was first theorized by Heinz Kasemir. As negatively charged leaders approach, increasing the localized electric field strength, grounded objects already experiencing corona discharge will exceed
5175-460: Is usually negatively charged, this is where most CG lightning originates. This region is typically at the elevation where freezing occurs within the cloud. Freezing, combined with collisions between ice and water, appears to be a critical part of the initial charge development and separation process. During wind-driven collisions, ice crystals tend to develop a positive charge, while a heavier, slushy mixture of ice and water (called graupel ) develops
5290-544: The Civilian Conservation Corps and Works Progress Administration . Lightning Lightning is a natural phenomenon formed by electrostatic discharges through the atmosphere between two electrically charged regions, either both in the atmosphere or one in the atmosphere and one on the ground , temporarily neutralizing these in a near-instantaneous release of an average of between 200 megajoules and 7 gigajoules of energy , depending on
5405-458: The Kelvin water dropper . The most likely charge-carrying species were considered to be the aqueous hydrogen ion and the aqueous hydroxide ion. The electrical charging of solid water ice has also been considered. The charged species were again considered to be the hydrogen ion and the hydroxide ion. An electron is not stable in liquid water concerning a hydroxide ion plus dissolved hydrogen for
5520-476: The triboelectric effect leading to electron or ion transfer between colliding bodies. Uncharged, colliding water-drops can become charged because of charge transfer between them (as aqueous ions) in an electric field as would exist in a thunder cloud. The main charging area in a thunderstorm occurs in the central part of the storm where air is moving upward rapidly (updraft) and temperatures range from −15 to −25 °C (5 to −13 °F); see Figure 1. In that area,
5635-584: The tropics where atmospheric convection is the greatest. This occurs from both the mixture of warmer and colder air masses , as well as differences in moisture concentrations, and it generally happens at the boundaries between them . The flow of warm ocean currents past drier land masses, such as the Gulf Stream , partially explains the elevated frequency of lightning in the Southeast United States . Because large bodies of water lack
5750-417: The 1840s as has the electrification of pure liquid water by the triboelectric effect. William Thomson (Lord Kelvin) demonstrated that charge separation in water occurs in the usual electric fields at the Earth's surface and developed a continuous electric field measuring device using that knowledge. The physical separation of charge into different regions using liquid water was demonstrated by Kelvin with
5865-433: The 1840s, with mustering points (yards and huts) occurring at Top Creek, (Sunderlands) Middle Yards, Kunderang, Left Hand, Oven Camp, Youdales Hut, Green Gully, Yarrowitch River and Front Tableland. The recently restored Middle Yards Hut was once part of the 32,000-hectare (79,000-acre) East Kunderang cattle station on the Macleay River. In the late 19th century several gold and antimony mines were established around
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#17327730449245980-857: The 33-kilometre (21 mi) difficult Long Point to Wollomombi overnight bushwalk. For the latter walk a vehicle drop-off and pick-up and suitable equipment are needed. Basic track notes are available from the NPWS Armidale office. Long Point has two formal lookouts along the Chandler View Circuit walk and Cassinia Walk offering views over the Chandler and Macleay Gorges. Facilities include a carpark, shelter shed with fireplace, picnic tables with small wood barbecues, tank water, pit toilets, an information display and bush camping with firewood supplied. 4WD vehicles are permitted to access Riverside, Youdales Hut and East Kunderang Homestead where
6095-605: The Apsley valley, but steep gorges blocked the way until they proceeded around the head of the Apsley Falls . After Oxley passed through the cedar-getters were the first white people to penetrate these remote gorges and valleys in search of Australian red cedar ( Toona ciliata ) which was floated down-river to Kempsey . There have been cattle grazing through the Macleay River Gorges, called 'The Falls', since
6210-607: The Congo , where the elevation is around 975 m (3,200 ft). On average, this region receives 158 lightning strikes per square kilometre per year (410/sq mi/yr). Other lightning hotspots include Singapore and Lightning Alley in Central Florida . According to the World Meteorological Organization , on April 29, 2020, a bolt 768 km (477.2 mi) long was observed in
6325-424: The Earth where lightning can damage or destroy them, cloud-to-ground (CG) lightning is the most studied and best understood of the three types, even though in-cloud (IC) and cloud-to-cloud (CC) are more common types of lightning. Lightning's relative unpredictability limits a complete explanation of how or why it occurs, even after hundreds of years of scientific investigation. About 70% of lightning occurs over land in
6440-716: The Green Gully area of Yarrowitch . Other species found in the park include bandicoots , bats , koalas , wombats and numerous small ground mammals. Quolls , common brushtail possums , sugar gliders , platypus , echidnas , wedge-tailed eagles , peregrine falcons and dingoes may also be seen. Over 173 bird species have been recorded in Oxley Wild Rivers National Park. There have been 38 reptile and 19 amphibian species recorded in Oxley Wild Rivers National Park. Skinks , goannas , tortoises , lizards , snakes , frogs and fish occur in
6555-554: The Macleay past East Kunderang Homestead in Oxley Wild Rivers National Park. The walk takes at least five days and all food and equipment has to be carried and there are numerous creek and river crossings, with some steep ascents and descents. This route generally takes at least four days to ride, and can be impassable after rain – check with Armidale or Walcha NPWS for details. Huts at Left Hand and Middle Yards are managed for their cultural heritage value, but are available for use while on
6670-530: The National Trail. The historic, remote Middle Yards Hut, located on Kunderang Brook deep within Oxley Wild Rivers National Park, has been restored to its original condition by the NPWS. A holding yard for horse trekkers was constructed here, along with a hitching rail, period furniture inside the hut, an outdoor barbecue and new water tank. Horses are not permitted at East Kunderang homestead. The Gara Gorge
6785-591: The Oxley Highway. The turnoff for this road is 19 kilometres (12 mi) past the Apsley Falls turnoff (travelling from Walcha). There are waterfalls, with two walking tracks taking in the Falls and Gorge Walk, being 1.5 kilometres (0.93 mi) return;, and the Tiara Walk, being 5 kilometres (3.1 mi) return, picnic facilities and bush camp sites are available for overnight stays. The Budds Mare campground
6900-529: The Park office, Walcha. The area caters for both picnickers and campers, with wood barbecues (wood provided), toilet and interpretation display at the hut. It's ideal for picnics, swimming and short walks. The East Kunderang Homestead is set on the banks of the Macleay River, 112 kilometres (70 mi) east of Armidale via Wollomombi and the Kempsey Road. Access to the homestead is along steep gravel roads and
7015-475: The Waterfall Way, visitors to the gorge are attracted by the rugged scenery, picnic sites, walks along the gorge rim trails, or hikes to the gorge riverbed. Facilities include drinking water, toilets, a shelter shed and fireplace and bush camp sites for overnight stays. The Dangars Gorge and Falls are located 22 kilometres (14 mi) south-east of Armidale along the Dangersleigh Road and are home to
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#17327730449247130-686: The area in 1818 and is one of the largest national parks in New South Wales. The park is part of the Hastings-Macleay Group World Heritage Site Gondwana Rainforests of Australia inscribed in 1986 and added to the Australian National Heritage List in 2007. The Oxley Wild Rivers National Park (OWRNP) was World Heritage listed in recognition of the extensive dry rainforest that occurs within
7245-631: The area includes the wedge-leaved guinea flower ( Hibbertia hermanniifolia ), Grevillea beadleana and Hakea fraseri (gorge hakea). Hillgrove spotted gum ( Eucalyptus michaeliana ) may be seen south of Hillgrove and in the Big Lease, north-east of Walcha. The beautiful Caladenia orchid has been spotted at Long Point. Dry rainforests in the OWRNP contain at least 187 plant species and they are visible as dense, dark green patches of brush box ( Lophostemon confertus ), favouring hollows where there
7360-437: The atmosphere, while creating nitrogen oxide and ozone at the same time. Lightning is also the major cause of wildfire, and wildfire can contribute to climate change as well. More studies are warranted to clarify their relationship. The details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. Electrification can be by
7475-402: The attachment process in progress. Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, there is a large drop in resistance across the lightning channel. Electrons accelerate rapidly as a result in a zone beginning at the point of attachment, which expands across the entire leader network at up to one third of
7590-425: The bark on its trunk which sheds to expose white, grey or bluish patches may also be seen, too. Epiphytic orchids may be observed growing in some of these trees, as well. The hazardous stinging tree ( Dendrocnide excelsa ) is found in various locations throughout the park. This is a dangerous plant and physical contact with it should be avoided. The stems and leaves are coated with fine hairs which when imbedded in
7705-530: The beautiful Dangars Falls, and the starting point for several great walks. McDirtys Walk - 6.9 km, 3 hours, medium difficulty. From the carpark at Dangars Gorge, cross the river and follow the track to the lookout above the falls (1.4 kilometres return), and Rock Wallaby Lookout (2.1 kilometres return). The track follows the gorge rim along a ridge to McDirtys Lookout (6.9 kilometres return). There are good places for picnics, camping and bushwalking. Salisbury Waters Walk - 14 km, 8 hours, difficult. This walk
7820-432: The cactus moth Cactoblastis cactorum within the park has facilitated the biological control of prickly pear. Feral cats and foxes occur in moderate numbers and can impact on native fauna. Wild dogs occur in the park and include dingoes, hybrids with domestic dogs. The National Parks and Wildlife Service give assistance to nearby landowners with respect to the control of these canine species. Wild dogs are controlled using
7935-432: The case of biased percolation, describes random connectivity phenomena, which produce an evolution of connected structures similar to that of lightning strikes. A streamer avalanche model has recently been favored by observational data taken by LOFAR during storms. When a stepped leader approaches the ground, the presence of opposite charges on the ground enhances the strength of the electric field . The electric field
8050-519: The cloud to the ground's surface. The actual discharge is the final stage of a very complex process. At its peak, a typical thunderstorm produces three or more strikes to the Earth per minute. Lightning primarily occurs when warm air is mixed with colder air masses, resulting in atmospheric disturbances necessary for polarizing the atmosphere. Lightning can also occur during dust storms , forest fires , tornadoes , volcanic eruptions , and even in
8165-476: The clouds. Also, given the very low probability of lightning striking the same point repeatedly and consistently, scientific inquiry is difficult even in areas of high CG frequency. In a process not well understood, a bidirectional channel of ionized air, called a " leader ", is initiated between oppositely-charged regions in a thundercloud. Leaders are electrically conductive channels of ionized gas that propagate through, or are otherwise attracted to, regions with
8280-424: The cold of winter, where the lightning is known as thundersnow . Hurricanes typically generate some lightning, mainly in the rainbands as much as 160 km (99 mi) from the center. Lightning is not distributed evenly around Earth . On Earth, the lightning frequency is approximately 44 (± 5) times per second, or nearly 1.4 billion flashes per year and the median duration is 0.52 seconds made up from
8395-431: The combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets (small water droplets below freezing), small ice crystals, and graupel (soft hail). The updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is considerably larger and denser, tends to fall or be suspended in the rising air. The differences in
8510-738: The country's state parks. The NASPD further counts over 43,000 miles (69,000 km) of trail, 217,367 campsites, and 8,277 cabins and lodges across U.S. state parks. The largest state park system in the United States is Alaska State Parks , with over 100 sites encompassing 3.3 million acres. Many states include designations beyond "state park" in their state parks systems. Other designations might be state recreation areas , state beaches, and state nature reserves . Some state park systems include long-distance trails and historic sites . To encourage tourism in rural areas, several states have simple lodges, inns, hotels, or motels (usually with
8625-427: The designation at all (such as the lodges of Georgia state parks ). The term "lodge" may also refer to a hiking lodge , essentially a large cabin for hikers rather than a large facility with private rooms and a restaurant. Other lodging may include yurts and tipis . Not all parks owned by a state are necessarily part of its state-park system, such as Stone Mountain Park near Atlanta. Some Texas state parks are
8740-549: The east coast and has dramatic gorges and waterfalls, extensive wilderness and dry rainforest. The main rivers in the national park are the: Apsley River, Macleay River, Wollomombi River, Chandler River , Tia River, Styx River, Gara River , Yarrowitch River, Oaky River and the Kunderang Brook. There are a number of waterfalls situated throughout the park including: Wollomombi Falls , Apsley Falls , Tia Falls and Dangars Falls as well as numerous cascades. The waterfalls in
8855-471: The east. Erosion by wind, rain, storms and ice over millions of years carved out the plateaus of the Northern Tablelands, and rivers and streams gradually cut back the eastern edge of the tableland creating deep gorges that eventually formed one continuous escarpment. The jagged scarp is slowly retreating west and this movement can be seen today in the erosion of steep cliffs at places like Wollomombi , Dangars and Apsley Gorges. The Apsley Macleay Gorges are
8970-456: The ground and tops up to 15 km (9.3 mi) in height. The place on Earth where lightning occurs most often is over Lake Maracaibo , wherein the Catatumbo lightning phenomenon produces 250 bolts of lightning a day. This activity occurs on average, 297 days a year. The second most lightning density is near the village of Kifuka in the mountains of the eastern Democratic Republic of
9085-495: The ground, the proportion of CG strikes (versus CC or IC discharges) becomes greater when the cloud is closer to the ground. In the tropics, where the freezing level is generally higher in the atmosphere, only 10% of lightning flashes are CG. At the latitude of Norway (around 60° North latitude), where the freezing elevation is lower, 50% of lightning is CG. Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2 km (0.62–1.24 mi) above
9200-405: The ground. Called step potentials, they are responsible for more injuries and deaths in groups of people or of other animals than the strike itself. Electricity takes every path available to it. Such step potentials will often cause current to flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes. The electric current of
9315-438: The ionic channel takes a comparatively long amount of time (hundreds of milliseconds ) in comparison to the resulting discharge, which occurs within a few dozen microseconds. The electric current needed to establish the channel, measured in the tens or hundreds of amperes , is dwarfed by subsequent currents during the actual discharge. Initiation of the lightning leader is not well understood. The electric field strength within
9430-408: The leaders can be readily observed in slow-motion videos of lightning flashes. It is possible for one end of the leader to fill the oppositely-charged well entirely while the other end is still active. When this happens, the leader end which filled the well may propagate outside of the thundercloud and result in either a cloud-to-air flash or a cloud-to-ground flash. In a typical cloud-to-ground flash,
9545-493: The local flora , fauna , geology , and cultural history of the area. These programs are designed not only to enhance the visitor experience but also to promote conservation awareness and encourage responsible enjoyment of natural resources. There are 6,792 state park units in the United States, according to the National Association of State Park Directors (NASPD). There are some 813 million annual visits to
9660-436: The lower part of the storm. The result is that the upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. The upward motions within the storm and winds at higher levels in the atmosphere tend to cause the small ice crystals (and positive charge) in the upper part of the thunderstorm cloud to spread out horizontally some distance from
9775-402: The most common species in the area. Because the conditions are extreme on the cliffs, quite a number of rare and uncommon shrubs are found there. These include: broadleaf hopbush ( Dodonaea rhombifolia ), Dodonaea serratifolia , Grevillea beadleana , Grevillea obtustiflora , Hakea fraseri (gorge hakea), climbing fig, orchids and Westringia sp. Bertya ingramii (narrow-leaved bertya)
9890-416: The movement of the precipitation cause collisions to occur. When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged; see Figure 2. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud. The larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward
10005-476: The national park. Further inclusions include Green Gully headwaters and 1,439 hectares (3,560 acres) of leasehold land in the lower Chandler River gorge. The Macleay Gorges Wilderness Area was declared in 1996 and extended in 1997 and covers over 50,000 hectares (120,000 acres), mainly in the central part of the park. In December 2009 a lightning strike started a bushfire in the Youdales Hut area. The hut
10120-426: The negative leader's connection with the ground. Positive leaders decay more rapidly than negative leaders do. For reasons not well understood, bidirectional leaders tend to initiate on the tips of the decayed positive leaders in which the negative end attempts to re-ionize the leader network. These leaders, also called recoil leaders , usually decay shortly after their formation. When they do manage to make contact with
10235-492: The north it is possible to see Round Mountain and Point Lookout. Heading to the right from the shelter shed is a track to a vantage point that overlooks Rusden Creek Gorge. There is a good 8-kilometre (5.0 mi) walk from here down the ridge to the Riverside Visitor Area on the Apsley River, but it is only for well prepared bushwalkers with a sound knowledge of steep country. Return up the same track or follow
10350-486: The park and also invaded rainforest thickets, where it has affected World Heritage values. Burrs of the Xanthium spp. are found on river flats, banks and associated tributaries. Blackberry, giant Parramatta grass, lantana and sweet briar ( Rosa rubiginosa ) are being controlled using herbicide . Spraying results have been encouraging but follow-up spraying is imperative to ensure long-term effectiveness. The release of
10465-500: The park are at their best after rains and the main ones are accessible by car. The formation of the area began with muddy sediments under ancient oceans that were changed by heat and pressure into hard rocks, then uplifted by movements of the continental plate and volcanic eruptions. This resulted in the formation of the Great Dividing Range , an undulating plateau that sloped gently to the west and fell away steeply to
10580-578: The park, and the associated rich biodiversity that includes several rare or threatened plants and animals. There are at least fourteen waterfalls in the park. For thousands of years, the Northern Tablelands and these valleys were the tribal lands of the Dangaddi aboriginal people, whose descendants are now concentrated in the lower Macleay River . Some marked trees have been found and a limestone cave shelter has been excavated near Kunderang Brook. In 1818 explorer John Oxley and his party tried to descend
10695-909: The park, particularly on the river flats. A number of fish species have been recorded. Notable, is the speckled longfin eel ( Anguilla reinhardtii ), which breeds in the ocean with the juveniles eventually returning to the Apsley–Macleay River system. Twelve species listed as threatened under the Threatened Species Conservation Act 1995 are found in the wilderness area. There are five mammals ( brush-tailed phascogale , brush-tailed rock wallaby , koala , squirrel glider and tiger quoll ); four birds ( glossy black cockatoo , greater sooty owl , superb fruit-dove and turquoise parrot ); one reptile ( Morelia spilota variegata (carpet python)); and two frogs ( Litoria piperata and Litoria subglandulosa ). The national park
10810-650: The park. There is a 52-metre (171 ft) steel stairway leading to an observation deck (with disabled access) where there are great views of the deep gorge and the falls. There are two large falls, with two walking tracks taking in the Gorge Rim Walk and the Oxley Walk, picnic facilities and camping area for overnight stays. On 28 December 2009 the steel footbridge leading to Gorge Rim Walk was washed away. The Tia Falls, located near Tia , 38 kilometres (24 mi) east of Walcha and 6 kilometres (3.7 mi) off
10925-470: The return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a ground-to-cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 100,000 km/s (one-third of
11040-542: The rim of the gorges, at places such as Halls Peak and Hillgrove , as well as two ambitious hydro-electric schemes to power them, the remains of which can be seen today along the Styx River and at Gara Gorge. In 1976 the Apsley Macleay Gorges were identified as being of true wilderness quality. At that stage the public protection offered to the area was limited to two small reserves in the south, and
11155-591: The road from Riverside up to the top. The return routes are a demanding climb, suitable for fit, experienced bushwalkers only, carrying ample provisions. Alternatively, a 4WD vehicle pick-up may be arranged at Riverside. Facilities here include: Campsites, toilets, picnic tables, wood barbecues, a supply of firewood. An extensive gorge, the Wollomombi Falls gorge houses two waterfalls: Wollomombi Falls itself (one of Australia's highest), and Chandler Falls. Located 40 kilometres (25 mi) east of Armidale along
11270-745: The route of the historic 1894 hydro-electric scheme, along old embankments and through ancient cuttings, to a lookout platform high above the river. Crombies Cave, the longest granite cave in Australia at 832 metres (2,730 ft), can be found in the next small creek, Powers Creek, an easy walk to the south of the Blue Hole. As the creek flows under the fence from the surrounding grazing country, within 20 metres (66 ft) it begins its journey underground to come out 832 metres (2,730 ft) down stream. The cave can be accessed from here and negotiated for at least half its length. It contains very beautiful granite sculptures, gnammas and potholes, some big caverns and
11385-561: The skin cause severe pain and irritation for prolonged periods. Smilax australis (lawyer vine or wait-a-while ) is another plant to be avoided as it has prickly climbing stems that are up to eight metres long and will catch in clothing or the skin. The understorey is often sparse except for occasional Acacia (wattles), Bursaria spinosa (blackthorn), Xanthorrhoea (grass trees) and The cassinia, geebung ( Persoonia spp.), Pomaderris lanigera (woolly pomaderris), Jacksonia scoparia (dogwood) and Prostanthera (mint bush) are
11500-545: The southern U.S.—sixty km (37 mi) longer than the previous distance record (southern Brazil, October 31, 2018). A single flash in Uruguay and northern Argentina on June 18, 2020, lasted for 17.1 seconds—0.37 seconds longer than the previous record (March 4, 2019, also in northern Argentina). In order for an electrostatic discharge to occur, two preconditions are necessary: first, a sufficiently high potential difference between two regions of space must exist, and second,
11615-404: The speed of light). The massive flow of electric current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 27,800 °C (50,000 °F), causing it to radiate with
11730-413: The speed of light. This is the "return stroke" and it is the most luminous and noticeable part of the lightning discharge. A large electric charge flows along the plasma channel, from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of
11845-474: The state line. Other multi-state parks are legally two separate parks with the same name and more informal cooperation between them. The title of oldest state park in the United States is claimed by Niagara Falls State Park in New York , established in 1885. Several public parks previously or currently maintained at the state level pre-date it. Indian Springs State Park has been operated continuously by
11960-454: The state of Georgia as a public park since 1825, although it did not gain the title "State Park" until 1931. In 1864 Yosemite Valley and Mariposa Grove were ceded by the federal government to California until Yosemite National Park was proclaimed in 1890. In 1878 Wisconsin set aside a vast swath of its northern forests as "The State Park" but, needing money, sold most of it to lumber companies within 20 years. Mackinac National Park
12075-451: The threatened brush-tailed rock-wallabies for food and shelter. The goats are controlled using ground and aerial shooting. Over 100 head of feral horses ( brumbies ) have been passively trapped in the Apsley catchment then re-homed. State park State parks are parks or other protected areas managed at the sub-national level within those nations which use "state" as a political subdivision. State parks are typically established by
12190-566: The thundercloud is not typically large enough to initiate this process by itself. Many hypotheses have been proposed. One hypothesis postulates that showers of relativistic electrons are created by cosmic rays and are then accelerated to higher velocities via a process called runaway breakdown . As these relativistic electrons collide and ionize neutral air molecules, they initiate leader formation. Another hypothesis involves locally enhanced electric fields being formed near elongated water droplets or ice crystals. Percolation theory , especially for
12305-495: The thunderstorm cloud base. This part of the thunderstorm cloud is called the anvil. While this is the main charging process for the thunderstorm cloud, some of these charges can be redistributed by air movements within the storm (updrafts and downdrafts). In addition, there is a small but important positive charge buildup near the bottom of the thunderstorm cloud due to the precipitation and warmer temperatures. The induced separation of charge in pure liquid water has been known since
12420-435: The time scales involved in thunderstorms. The charge carrier in lightning is mainly electrons in a plasma. The process of going from charge as ions (positive hydrogen ion and negative hydroxide ion) associated with liquid water or solid water to charge as electrons associated with lightning must involve some form of electro-chemistry, that is, the oxidation and/or the reduction of chemical species. As hydroxide functions as
12535-406: The topographic variation that would result in atmospheric mixing, lightning is notably less frequent over the world's oceans than over land. The North and South Poles are limited in their coverage of thunderstorms and therefore result in areas with the least lightning. In general, CG lightning flashes account for only 25% of all total lightning flashes worldwide. Since the base of a thunderstorm
12650-570: The track to the Apsley River at Riverside was improved and Elcom installed a river gauging station. The project was shelved following a land use study recommending a national park be established. In 1986 the park was gazetted to foster nature conservation, cultural heritage and tourism on the Northern Tablelands. In 1989 East Kunderang Station of 30,400 hectares (75,000 acres) passed to the National Parks and Wildlife Service (NPWS) and
12765-559: The type. This discharge may produce a wide range of electromagnetic radiation , from heat created by the rapid movement of electrons , to brilliant flashes of visible light in the form of black-body radiation . Lightning causes thunder , a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms as well as other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions . Lightning
12880-409: Was drowned in 1900 while returning on horseback from the mail run. The homestead may be booked for up to ten people for a minimum of two nights. Marys View, a lookout situated on a bluff about 3 kilometres (1.9 mi) south east of East Kunderang homestead, has perhaps the best view of any lookout of the Macleay Gorges. This lookout can be accessed as a day walk from East Kunderang. From here you have
12995-473: Was established in 1875 as the second U.S. national park before being converted to a state park in 1895. The first state park with the designation of "state park" was Itasca State Park in Minnesota , established in 1891. Many state park systems date to the 1930s, when around 800 state parks (and several national ones) across the country were developed with assistance from federal job-creation programs like
13110-762: Was proclaimed the Oxley Wild Rivers National Park. In 1994 Oxley Wild Rivers National Park was inscribed on the Register of World Heritage sites, as part of the Central Eastern Rainforest Reserves of Australia (CERRA); subsequently renamed as the Gondwana Rainforests of Australia. Later 1,850 hectares (4,600 acres) of Winterbourne State Forest, also known at the Big Lease, was added to the wilderness. The remaining 1,560 hectares (3,900 acres) of Winterbourne and 1,075 hectares (2,660 acres) of Enmore State Forests are to be added to
13225-530: Was unaffected, but 1,500 hectares (3,700 acres) of inaccessible steep country was burnt out before it was brought under control. Another lightning strike started a large bushfire in the Reedy Creek region of the park. This fire has burnt out over 8,000 hectares (20,000 acres) of rough country. The Oxley Wild Rivers National Park lies along the Great Escarpment between the Northern Tablelands, and
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