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83-898: Kohala may refer to: Kohala (mountain) an extinct volcano of Hawaii Kohala, Hawaii , two districts on the island of Hawaii Kohala, Pakistan , a town in Pakistan Kohala Bridge , a bridge between Azad Kashmir and Pakistan Kohala Hydropower Project Pakistan Kohala, Jalandhar a village in Punjab, India Kohala, Mysore , a village in Karnataka, India Kohala, Estonia , village in Rakvere Parish, Lääne-Viru County, Estonia Hans Kohala (born 1966), Swedish athlete See also [ edit ] Koala (disambiguation) [REDACTED] Topics referred to by

166-413: A landslide destroyed the northeast flank of the volcano, reducing its height by over 1,000 m (3,300 ft) and traveling 130 km (81 mi) across the sea floor . This huge landslide may be partially responsible for the volcano's foot-like shape. Marine fossils have been found on the flank of the volcano, far too high to have been deposited by standard ocean waves . Analysis indicated that

249-409: A defined barometric pressure . Generally, the pressure used to set the altimeter is the barometric pressure that would exist at MSL in the region being flown over. This pressure is referred to as either QNH or "altimeter" and is transmitted to the pilot by radio from air traffic control (ATC) or an automatic terminal information service (ATIS). Since the terrain elevation is also referenced to MSL,

332-432: A few metres, in timeframes ranging from minutes to months: Between 1901 and 2018, the average sea level rose by 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s. This was faster than the sea level had ever risen over at least the past 3,000 years. The rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022. Climate change due to human activities

415-442: A flat crater floor surrounded by cones and fault scarps, the main caldera is affected relatively little by erosion from water. Most of Kohala's summit groundwater ends up in either Waipi'o or Honokane Nui; the enormous amount of water routed through these valleys results in a large amount of water erosion , which causes the valley walls to frequently collapse, accelerating valley development. This abundance of surface water inspired

498-399: A primary factor in the development of the largest valleys, the dike complex plays another important role —that of creating and maintaining the water table . Hawaiian lava is extremely permeable and porous . Rainwater easily seeps into the lava, creating a large lens of fresh water below the island surface. In most places, the top of the water table is just a few feet from sea level, as

581-438: A reference datum for mean sea level (MSL). It is also used in aviation, where some heights are recorded and reported with respect to mean sea level (contrast with flight level ), and in the atmospheric sciences , and in land surveying . An alternative is to base height measurements on a reference ellipsoid approximating the entire Earth, which is what systems such as GPS do. In aviation, the reference ellipsoid known as WGS84

664-425: A series of stone paths that divided the farmed area into plots of variable size. These structures are unique because although many people used such systems at the time, Kohala has some of the few to survive. The leeward slopes of Kohala were used for sugarcane plantations in the late 19th century. The trip from the fields to the mills and then boats was mechanized by steam locomotive in 1883. Several plantations on

747-470: A sharp reduction in greenhouse gas emissions, this may increase to hundreds of millions in the latter decades of the century. Local factors like tidal range or land subsidence will greatly affect the severity of impacts. For instance, sea level rise in the United States is likely to be two to three times greater than the global average by the end of the century. Yet, of the 20 countries with

830-415: A thick layer of ferns and mosses carpeting the floor, which act as sponges, absorbing water from rain and passing much of it through to the groundwater in aquifers below; when feral animals like pigs trample the covering, the forest loses its ability to hold in water effectively, and instead of recharging the aquifer, it results in a severe loss of topsoil , much of which ends up being dumped by streams into

913-406: A very high ratio of the species present being found nowhere else on Earth. Only about 2.5% of the world's rainforest is cloud rainforest, making it a unique habitat as well. The mountain supports approximately 155 native species of vertebrates , crustaceans , mollusks , and plants . A diverse complexion of fungi , liverwort , and mosses further add to the variety. In fact, up to a quarter of

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996-642: Is "to respectfully engage the Island of Hawaiʻi as an extraordinary and vibrant research and learning laboratory for humanity." The land around Kohala is administered as two districts, North Kohala and South Kohala, of the County of Hawaiʻi . The beaches, parks, golf courses, and resorts in South Kohala are called "the Kohala Coast." King Kamehameha I , the first King of the unified Hawaiian Islands ,

1079-400: Is a small string of faults on and near the main summit caldera , arranged parallel to the northern coast. The faults were originally regarded to be a direct result of the collapse; however scientists note the fault lines do not go all the way to the coast but are arranged tightly clustered around the caldera. This indicates that the fault lines may have been caused indirectly, possibly due to

1162-417: Is an average surface level of one or more among Earth 's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum  – a standardised geodetic datum  – that is used, for example, as a chart datum in cartography and marine navigation , or, in aviation, as the standard sea level at which atmospheric pressure

1245-488: Is because the sea is in constant motion, affected by the tides, wind , atmospheric pressure, local gravitational differences, temperature, salinity , and so forth. The mean sea level at a particular location may be calculated over an extended time period and used as a datum . For example, hourly measurements may be averaged over a full Metonic 19-year lunar cycle to determine the mean sea level at an official tide gauge . Still-water level or still-water sea level (SWL)

1328-549: Is believed that bogs form in low-lying areas where clay in the soil prevents proper water drainage, resulting in an accumulation of water that impedes the root systems of woody plants . Kohala's bogs are characterized by sedges , mosses of the genus Sphagnum , and oha wai, native members of the bellflower family. Other habitats include rain forest and mesophytic (wet) forests. The same isolation that produced Kohala's unique ecosystem also makes it very vulnerable to invasive species . Alien plants and feral animals are among

1411-415: Is different from Wikidata All article disambiguation pages All disambiguation pages Kohala (mountain) Kohala is a shield volcano cut by multiple deep gorges , which are the product of thousands of years of erosion . Unlike the typical symmetry of other Hawaiian volcanoes, Kohala is shaped like a foot. Toward the end of its shield-building stage 250,000 to 300,000 years ago,

1494-427: Is due to change in either the volume of water in the world's oceans or the volume of the oceanic basins . Two major mechanisms are currently causing eustatic sea level rise. First, shrinking land ice, such as mountain glaciers and polar ice sheets, is releasing water into the oceans. Second, as ocean temperatures rise, the warmer water expands. Many factors can produce short-term changes in sea level, typically within

1577-483: Is increasingly used to define heights; however, differences up to 100 metres (328 feet) exist between this ellipsoid height and local mean sea level. Another alternative is to use a geoid -based vertical datum such as NAVD88 and the global EGM96 (part of WGS84). Details vary in different countries. When referring to geographic features such as mountains, on a topographic map variations in elevation are shown by contour lines . A mountain's highest point or summit

1660-512: Is measured to calibrate altitude and, consequently, aircraft flight levels . A common and relatively straightforward mean sea-level standard is instead a long-term average of tide gauge readings at a particular reference location. Sea levels can be affected by many factors and are known to have varied greatly over geological time scales . Current sea level rise is mainly caused by human-induced climate change . When temperatures rise, mountain glaciers and polar ice sheets melt, increasing

1743-471: Is mostly 260,000 to 140,000 years old, and composed mainly of hawaiite and trachyte . The separation between the two layers is not clear; the lowest layers may actually be in the Pololu section, based on their depositional patterns and low phosphorus content. The time intervals separating the two periods of volcanic evolution were extremely brief, something first noted in 1988. The forest-covered summit of

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1826-450: Is the level of the sea with motions such as wind waves averaged out. Then MSL implies the SWL further averaged over a period of time such that changes due to, e.g., the tides , also have zero mean. Global MSL refers to a spatial average over the entire ocean area, typically using large sets of tide gauges and/or satellite measurements. One often measures the values of MSL with respect to

1909-727: Is the main cause. Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise , with another 42% resulting from thermal expansion of water . Sea level rise lags behind changes in the Earth 's temperature by many decades, and sea level rise will therefore continue to accelerate between now and 2050 in response to warming that has already happened. What happens after that depends on human greenhouse gas emissions . If there are very deep cuts in emissions, sea level rise would slow between 2050 and 2100. It could then reach by 2100 slightly over 30 cm (1 ft) from now and approximately 60 cm (2 ft) from

1992-531: Is typically illustrated with the AMSL height in metres, feet or both. In unusual cases where a land location is below sea level, such as Death Valley, California , the elevation AMSL is negative. It is often necessary to compare the local height of the mean sea surface with a "level" reference surface, or geodetic datum, called the geoid . In the absence of external forces, the local mean sea level would coincide with this geoid surface, being an equipotential surface of

2075-622: The geoid of the Earth, which approximates the local mean sea level for locations in the open ocean. The geoid includes a significant depression in the Indian Ocean , whose surface dips as much as 106 m (348 ft) below the global mean sea level (excluding minor effects such as tides and currents). Precise determination of a "mean sea level" is difficult because of the many factors that affect sea level. Instantaneous sea level varies substantially on several scales of time and space. This

2158-418: The height above mean sea level (AMSL). The term APSL means above present sea level, comparing sea levels in the past with the level today. Earth's radius at sea level is 6,378.137 km (3,963.191 mi) at the equator. It is 6,356.752 km (3,949.903 mi) at the poles and 6,371.001 km (3,958.756 mi) on average. This flattened spheroid , combined with local gravity anomalies , defines

2241-565: The 16 smaller streams between Waikoloa Stream and the Wailoa river in Waipi'o Valley. The natural habitats in the Kohala district range across a wide rainfall gradient in a very short distance—from less than 5 in (130 mm) a year on the coast near Kawaihae, to more than 150 in (3,800 mm) a year near the summit of Kohala Mountain, a distance of just 11 mi (18 km). At

2324-562: The 1690s. Satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES , TOPEX/Poseidon was followed by Jason-1 in 2001 and the Ocean Surface Topography Mission on the Jason-2 satellite in 2008. Height above mean sea level ( AMSL ) is the elevation (on the ground) or altitude (in the air) of an object, relative to

2407-973: The 19th century. With high emissions it would instead accelerate further, and could rise by 1.0 m ( 3 + 1 ⁄ 3  ft) or even 1.6 m ( 5 + 1 ⁄ 3  ft) by 2100. In the long run, sea level rise would amount to 2–3 m (7–10 ft) over the next 2000 years if warming stays to its current 1.5 °C (2.7 °F) over the pre-industrial past. It would be 19–22 metres (62–72 ft) if warming peaks at 5 °C (9.0 °F). Rising seas affect every coastal and island population on Earth. This can be through flooding, higher storm surges , king tides , and tsunamis . There are many knock-on effects. They lead to loss of coastal ecosystems like mangroves . Crop yields may reduce because of increasing salt levels in irrigation water. Damage to ports disrupts sea trade. The sea level rise projected by 2050 will expose places currently inhabited by tens of millions of people to annual flooding. Without

2490-448: The Earth's gravitational field which, in itself, does not conform to a simple sphere or ellipsoid and exhibits gravity anomalies such as those measured by NASA's GRACE satellites . In reality, the geoid surface is not directly observed, even as a long-term average, due to ocean currents, air pressure variations, temperature and salinity variations, etc. The location-dependent but time-persistent separation between local mean sea level and

2573-456: The Kohala watershed and to protect it from threats, most especially invasive species. Another project to raise awareness of Kohala's ecosystem is The Kohala Center , an independent, not-for-profit , community-based organization for research and education. It was established as a response to requests by island residents to create an educational and employment opportunity related to Hawaii's natural and cultural significance. The center's mission

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2656-661: The Leeward side of the volcano for centuries. The northern part of the island is named after the mountain, with two districts named North and South Kohala. King Kamehameha I , the first King of the Kingdom of Hawaii , was born in North Kohala , near Hawi . Studies of the volcano's lava accumulation rate have put the volcano's age at somewhere near one million years. It is believed to have breached sea level more than 500,000 years ago. Beginning 300,000 years ago,

2739-705: The Marégraphe in Marseilles measures continuously the sea level since 1883 and offers the longest collated data about the sea level. It is used for a part of continental Europe and the main part of Africa as the official sea level. Spain uses the reference to measure heights below or above sea level at Alicante , while the European Vertical Reference System is calibrated to the Amsterdam Peil elevation, which dates back to

2822-770: The actual valley walls at the seashore range from 300 m (1,000 ft) at the Waipiʻo Valley Lookout at the southeastern corner of Kohala mountain, to a high of over 500 m (1,600 ft) in Honopue, then diminishing to less than 150 m (490 ft) at Pololu Lookout at the northern end of the valleys. In the back, deeper in the mountain, all of the valleys have sheer walls well in excess of 1,000 m (3,300 ft). Numerous spectacular waterfalls cascade or fall over these cliffs. Some, such as Hi'ilawe Falls in Waipi'o valley, have single drops exceeding 300 m (1,000 ft). The volcano stayed active well into

2905-456: The amount of water in the oceans, while the existing seawater also expands with heat. Because most of human settlement and infrastructure was built in response to a more-normalized sea level with limited expected change, populations affected by sea level rise will need to invest in climate adaptation to mitigate the worst effects or, when populations are at extreme risk, a process of managed retreat . The term above sea level generally refers to

2988-494: The base of the volcano 6 km (3.7 mi) inshore. A research team led by University of Hawaii's Gary McMurtry and Dave Tappin of the British Geological Survey found that the fossils had been deposited by a massive tsunami , 61 m (200 ft) above the current sea level. The team dated the fossils and nearby volcanic rock at about 120,000 years old. Based on the rate of Kohala's subsidence over

3071-514: The coast are remnants of dry forests , and near the summit lies a cloud forest , a type of rainforest that obtains much of its moisture from "cloud drip" in addition to precipitation . These large cloud forests dominate its slopes. This biome is rare, and contains a disproportionate percentage of the world's rare and endemic species. The soil at Kohala is nitrogen-rich , facilitating root growth . The happy combination of small trees, bushes, ferns, vines, and other forms of ground cover keep

3154-630: The first of Kohala's three massive irrigation diversion "ditches", the Upper Hamakua Ditch, although the water was initially used for transporting ("fluming") sugarcane to the mills rather than irrigation. Surface water supplies, however, were not stable enough for the large scale plantation economy developing in Hamakua and North Kohala, so later ditches tapped the spring fed base flows of the valleys and larger gulches. Only Waimanu Valley escaped with none of its tributaries tapped, along with

3237-401: The flanks of the volcano. North of Kohala's summit the volcano's northwest–southeast trending rift zone separates rainfall into two streams, going southeast, into Waipiʻo Valley, or northwest, into Honokane Nui Valley. When the volcano was still active, vertical sheets of magma, arranged in what is known as dikes , forced their way out of the magma reservoir and intruded into the rift zone, which

3320-416: The formation of these mountainside valleys, as illustrated by later Pololu lava flows, which covered the north and northwestern end of Kohala volcano and often flowed into Pololu Valley . Recent seafloor mapping seems to show that the valley extends a short way beyond the seashore, then terminates at what may be the headwall of the great landslide found off the northeast coast of Kohala. In addition to being

3403-404: The fossils had been deposited by a massive tsunami approximately 120,000 years ago. Because it is so far from the nearest major landmass, the ecosystem of Kohala has experienced geographic isolation , resulting in a unique ecosystem. There are several initiatives to preserve this ecosystem against invasive species. Crops, especially sweet potato (Ipomoea batatas) , have been cultivated on

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3486-399: The fresh water lens is floating on salt water. Unlike porous lava flows, however, dikes cool underground into dense rock with few cracks and vesicles . The dikes act as impermeable vertical walls through which groundwater cannot flow. Deep layers of ash compact into impermeable layers between lava flows, preventing percolation of the rainwater. Rainwater that would ordinarily seep right through

3569-482: The geoid is referred to as (mean) ocean surface topography . It varies globally in a typical range of ±1 m (3 ft). Several terms are used to describe the changing relationships between sea level and dry land. The melting of glaciers at the end of ice ages results in isostatic post-glacial rebound , when land rises after the weight of ice is removed. Conversely, older volcanic islands experience relative sea level rise, due to isostatic subsidence from

3652-634: The greatest exposure to sea level rise, twelve are in Asia , including Indonesia , Bangladesh and the Philippines. The resilience and adaptive capacity of ecosystems and countries also varies, which will result in more or less pronounced impacts. The greatest impact on human populations in the near term will occur in the low-lying Caribbean and Pacific islands . Sea level rise will make many of them uninhabitable later this century. Pilots can estimate height above sea level with an altimeter set to

3735-472: The greatest threats to the local ecology. Plants like the kahili ginger (Hedychium gardnerianum) and the strawberry guava (Psidium cattleinum) displace native species. Prior to human settlement, many major organisms such as conifers and rodents never made it onto the island, so the ecosystem never developed defenses against them, leaving Hawaii vulnerable to damage by hoofed animals , rodents, and predation . Kohala's native Hawaiian rain forest has

3818-419: The ground gets trapped in the dike "reservoirs," located well above sea level. The groundwater is confined to a flow along the dike until it finds a means to escape. In Kohala, the numerous dikes near the summit inhibit groundwater from seeping downslope to the northeast, where it naturally wants to go. Rather, the Kohala dike complex guides it northwest or southeast, down the axis of the rift zones, just like

3901-555: The height of planetary features. Local mean sea level (LMSL) is defined as the height of the sea with respect to a land benchmark, averaged over a period of time long enough that fluctuations caused by waves and tides are smoothed out, typically a year or more. One must adjust perceived changes in LMSL to account for vertical movements of the land, which can occur at rates similar to sea level changes (millimetres per year). Some land movements occur because of isostatic adjustment to

3984-504: The higher elevations and distribute it to the then-extensive sugarcane industry. In 1905, after 18 months and the loss of 17 lives, the Kohala Ditch, a vast network of flumes and ditches, measuring 22 mi (35 km) in length, was completed. It has since come into use by ranches, farms, and homes. A portion of the ditch became a tourist attraction until it was damaged by the 2006 Kiholo Bay earthquake , centered just southwest of

4067-591: The land; hence a change in relative MSL or ( relative sea level ) can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates, or both. In the UK, the ordnance datum (the 0 metres height on UK maps) is the mean sea level measured at Newlyn in Cornwall between 1915 and 1921. Before 1921, the vertical datum was MSL at the Victoria Dock, Liverpool . Since

4150-435: The last 780,000 years. Radiometric dating ranged mostly from 450,000 to 320,000 years ago, although several pieces strayed lower; this indicated a period of eruptive history at the time. Kohala was devastated by a massive landslide between 250,000 and 300,000 years before present . Debris from the slide was found on the ocean floor up to 130 km (81 mi) away from the volcano. Twenty kilometers wide at

4233-401: The lava flows that formed it; however, the northwest shoreline boasts some of the highest seacliffs on Earth. Events during and after its eruptions give the volcano several unique geomorphic features, some possibly resulting from the ancient collapse and landslide. The volcano is shaped like a foot; the northeast coast is prominently indented across 20 km (12 mi) of shoreline. There

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4316-411: The life cycle of Hawaiian volcanoes. The United States Geological Survey has assessed the extinct Kohala as a low-risk area. The volcano is in zone 9 (bottom risk), while the border of the volcano with Mauna Kea is zone 8 (second lowest), as Mauna Kea has not produced lava flows for 4,500 years. Kohala, like other shield volcanoes, has a shallow surface slope due to the low viscosity of

4399-481: The melting of ice sheets at the end of the last ice age . The weight of the ice sheet depresses the underlying land, and when the ice melts away the land slowly rebounds . Changes in ground-based ice volume also affect local and regional sea levels by the readjustment of the geoid and true polar wander . Atmospheric pressure , ocean currents and local ocean temperature changes can affect LMSL as well. Eustatic sea level change (global as opposed to local change)

4482-543: The mountain slope. Instead, the rainwater flows down laterally and empties into the back of what have thus become the largest valleys (Waipiʻo and Honokane Nui). The leeward northwestern slope of Kohala has few stream valleys cut into it, the result of the rain shadow effect, as the dominant trade winds bring most of the rainfall to the northeastern slope of the volcano. The seven windward valleys of Kohala are, from southeast to northwest, Waipiʻo, Waimanu, Honopue, Honokea, Honokane Iki, Honokane Nui, and Pololu. The size of

4565-553: The mountain were consolidated into the Kohala Sugar Company by 1937. At the peak of its production, the company had 600 employees, 13,000 acres (20 sq mi) of land, and a capacity of 45,000 t (99,000,000 lb) of raw sugar per year. In 1975 the company finally closed down. Kohala supports a very complex hydrological cycle . In the early part of the 20th century, this was exploited by building surface irrigational channels designed to capture water at

4648-504: The mountain. The Hawaii County Department of Water Supply relies on streams from Kohala to supply water to the population of the island. With increasing demand, the original surface channels have been supplemented by deep wells designed to channel groundwater for domestic use. In 2003 the Kohala Watershed Partnership was formed, a voluntary group of private land owners and state managers, designed to help manage

4731-513: The nearby Mauna Kea and reappears further southeast in the Hilo Ridge , as indicated by the relationship between collected lava samples. In addition, the two features align to one another more closely than does the ridge to Mauna Kea, of which it was once thought to constitute a part. The bulk of the ridge is built of volcanic rock with reverse magnetic polarity, evidence that the volcano is at least 780,000 years old. Older lava dated from

4814-421: The ocean. There is evidence of pre-modern agriculture on the leeward slopes of Kohala. From 1400 to 1800, the principal crop grown at Kohala was sweet potato (Ipomoea batatas) , although there is also evidence of yams (Dioscorea sp.) , taro (Colocasia esculenta) , bananas (Musa hybrids) , sugarcane (Saccharum officinarum) , and gourds of the family Cucurbitaceae . The optimal rainfall level for

4897-433: The original size and shape of the volcano, as the southeast flank has been buried by volcanic lava flows from nearby Mauna Kea and Mauna Loa . However, based on a sharp increase of incline on the submarine slope of the volcano at a depth of 1,000 m (3,300 ft), scientists estimate that in its prime the portion of Kohala that was above the water was more than 50 km (31 mi) wide. Geologists estimate that

4980-462: The past 475,000 years, it was estimated that the fossils were deposited at a height of about 500 m (1,600 ft), well out of reach of storms and far above the normal sea level at the time. The timing corresponds with the last great landslide of nearby Mauna Loa . Researchers hypothesize that the underwater landslide from the nearby volcano triggered a gigantic tsunami, which swept up coral and other small marine organisms, depositing them on

5063-402: The plants in the forest are mosses and ferns . These work to capture the water from clouds, in turn providing microhabitats for invertebrates and amphibians , and their predators. Estimates on the water capacity of the forest range from 320 to 1,600 US gal/acre (3,000 to 15,000 L/ha). The mountain is also home to several bogs , which exist as breaks in the cloud forests. It

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5146-423: The rate of eruption slowly decreased over a long period of time to a point where erosion wore the volcano down faster than Kohala rebuilt itself through volcanic activity. Decreasing eruptions combined with increasing erosion caused Kohala to slowly weather away and subside into the ocean. The oldest lava flows that are still exposed at the surface are just under 780,000 years old. It is difficult to determine

5229-424: The same term This disambiguation page lists articles about distinct geographical locations with the same name. If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Kohala&oldid=1163505070 " Category : Place name disambiguation pages Hidden categories: Short description

5312-484: The sea rapidly in the form of destructive floods, is fed gradually to the springs and to the underground artesian basins where it is held for use over a much longer interval... C S Judd, Superintendent of Forestry in Hawaiʻi, 1924 The forest lies perpendicular to the prevailing trade winds, a characteristic that leads to frequent cloud formation and abundant rainfall. Thus the rain forests carpeting Kohala are vital to

5395-420: The shoreline, the landslide cut back to the summit of the volcano, and is partially, if not largely, responsible for the volcano losing 1,000 m (3,300 ft) in height since then. The famous sea cliffs of the windward Kohala shoreline stand as evidence of the massive geologic disaster, and mark the topmost part of the debris from this ancient landslide. There are also several other unique features found on

5478-427: The soil porous and allow the water to percolate more easily into underground channels. The foliage of the trees breaks the force of rain and prevents the impact of soil by raindrops. A considerable portion of the precipitation is let down to the ground slowly by this three-story cover of trees, bushes, and floor plants and in this manner the rain, falling on a well-forested area, is held back and instead of rushing down to

5561-400: The sudden release of stress during the event. Mauna Kea causes the trade winds to divert around it, increasing wind to super-enhanced flow over the Kohala ridge and orographic lift brings most of the rainfall to the northeastern slope of Kohala. The windward side of Kohala mountain is dissected by multiple, deeply eroded stream valleys in a southwest–northeast alignment, cutting into

5644-499: The supply of groundwater on the island. The role of Kohala's ecosystem in supporting water flow has long been recognized. As early as 1902, US Forester E. M. Griffith wrote "Forest protection means not only increasing the rainfall, but more important still, conserving the water supply. The future welfare and agricultural prosperity of the Hawaiian Islands depends upon the preservation of the forest." Before humans arrived,

5727-414: The surface water. On the other hand, the three smaller valleys between the large ones - Honopue, Honokea, and Honokane Iki - as well as the many smaller gulches which are not yet valleys, are deprived of groundwater by the orientation of the rift zone and its dikes. Without the large amount of water that is received by the bigger valleys, these valleys grow far more slowly. Due to its topography as essentially

5810-496: The sweet potato lies between 30 and 50 inches (76–127 cm) per year. A combination of factors makes the rainfall at Kohala variable both from location to location and from year to year. In addition, Kohala is buffeted by strong winds, which are directly correlated to soil erosion; ancient farmers utilized a series of earthen embarkments and stone walls to protect their crops. This technique has been shown to reduce wind by at least 20–30 percent. In addition to walls, there are

5893-549: The third largest valley, has its drainage almost exclusively from the north side of the summit, and as a result is a deep, long, narrow bottomed valley with little habitable floodplain. The remaining valleys derive all their water from the lower northeastern slopes of the volcano, and as a result are smaller. In addition, there are innumerable gulches of various depths which have not yet reached sea level and began to form flood plains, becoming valleys. Still, some of these are more than 300 m (1,000 ft) in depth. The depth of

5976-518: The times of the Russian Empire , in Russia and its other former parts, now independent states, the sea level is measured from the zero level of Kronstadt Sea-Gauge. In Hong Kong, "mPD" is a surveying term meaning "metres above Principal Datum" and refers to height of 0.146 m (5.7 in) above chart datum and 1.304 m (4 ft 3.3 in) below the average sea level. In France,

6059-415: The toe of the ridge was estimated to be roughly between 1.1 and 1.2 million years old. Geologists have classified the volcano's lava flows into two units. The Hawi Volcanic layers were deposited in the postshield stage of the volcano's life, and the younger Pololu Volcanics were deposited in the volcano's shield-building stage. The rock in the younger Hawi section, which overlies the older Pololu flows,

6142-428: The valleys reflects the amount of drainage they have been able to capture; Waipiʻo, the largest, at some point drained Waimanu Valley as well, and the former headwaters of Waimanu are now one of its branches. Waimanu valley, cut off from its headwaters to the summit and left with Wai'ilikahi as its main tributary, still had managed to form a substantial floodplain, although less than half the size of Waipiʻo. Honokane Nui,

6225-460: The volcano consists of many cones which generated lava from its two rift zones between 240,000 and 120,000 years ago. Kohala completed its shield-building stage 245,000 years ago and has been in decline ever since. Potassium-argon dating indicates that the volcano last erupted about 120,000 years ago in the late Pleistocene . Kohala is currently in transition between the postshield and erosional Hawaiian volcanic stages in

6308-516: The volcano was once about twice its current size. The volcano is so old that it experienced, and recorded, a reversal of magnetic polarity (a change in the orientation of Earth's magnetic field so that the positions of the North and South poles interchange) that happened 780,000 years ago. Fifty flow units in the top 140 m (460 ft) of exposed strata in the Pololu section are of normal polarity, indicating that they were deposited within

6391-423: The volcano, all marks made by the decimating collapse. Kohala is thought to have last erupted 120,000 years ago. However, several samples of a more recent date have been obtained. Two samples collected about 120 m (390 ft) apart, obtained from Waipiʻo Valley on the volcano's east flank in 1977, were dated reliably to 60,000 years. Another double set of samples, collected from the western part in 1996,

6474-411: The weight of cooling volcanos. The subsidence of land due to the withdrawal of groundwater is another isostatic cause of relative sea level rise. On planets that lack a liquid ocean, planetologists can calculate a "mean altitude" by averaging the heights of all points on the surface. This altitude, sometimes referred to as a "sea level" or zero-level elevation , serves equivalently as a reference for

6557-447: The western face of Kohala. Mauna Loa, an active volcano, has since repaired its flank. Marine geologist Tappin believes that a "future collapse on this volcano, with the potential for mega-tsunami generation, is almost certain." Kohala had two active rift zones , a characteristic common to Hawaiian volcanoes. The double ridge, shaped axially , was active in both the shield and postshield stages. The southeast rift zone passes under

6640-474: The wildlife population at Kohala and on the rest of the island was isolated from other species, as it was separated from the nearest major landmass by over 2,000 mi (3,200 km) of open water. The early colonizers of Kohala came by wind, storm or floating on the ocean. Successful colonizations occur on the magnitude of once every 35,000 years. The 2,000 successful ancestors that arrived at Kohala evolved into about 8,500 to 12,500 unique species, resulting in

6723-872: Was born near Upolu Point , the northern tip of Kohala. The site is within Kohala Historical Sites State Monument . The original Kamehameha Statue stands in front of the community center in Kapaʻau , and replicas of the statue are found at Aliʻiōlani Hale in Honolulu , and in Emancipation Hall at the United States Capitol Visitor Center in Washington, D.C. Sea level Mean sea level ( MSL , often shortened to sea level )

6806-552: Was measured to be 80,000 years in age. The samples have been treated with skepticism by the scientific community, and their ages have been directly challenged. The rocks collected from the west site have not been tested by subsequent experiments. The lava samples collected from the eastern site were allegedly found under a Mauna Loa lava flow, which had been previously dated to 187,000 years. The Kohala lava flows could be as young as 120,000 years although they may be even younger. In 2004, unidentified marine fossils were found at

6889-403: Was weakened by the collapse. As the dikes forced their way up, they formed fractures and faults parallel to the rift zone. The exertion caused by the dikes produced a series of faults along its length, forming horsts and grabens ( fault blocks ). Northeast of the Kohala summit, where the most rainfall occurs, the faulted structure prevents summit rainwater from naturally flowing northeast down

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