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96-482: Although only 47 miles long, the Robert Frost Trail takes in a diverse patchwork of habitats, terrain, and scenery. The trail traverses trap rock Metacomet Ridge with its microclimate ecosystems; wetland habitat; ponds; farmland; deep ravines; wooded ledges; river banks; reservoirs; historic mill ponds; and dense forests. One segment of the trail follows a narrow greenway that successfully weaves through

192-630: A bolide impact, for which an impact crater containing Manicouagan Reservoir in Quebec , Canada , has been singled out. However, the Manicouagan impact melt has been dated to 214±1 Mya. The date of the Triassic-Jurassic boundary has also been more accurately fixed recently, at 201.4 Mya. Both dates are gaining accuracy by using more accurate forms of radiometric dating, in particular the decay of uranium to lead in zircons formed at time of

288-626: A cosmopolitan distribution . Coelacanths show their highest post- Devonian diversity in the Early Triassic . Ray-finned fishes (actinopterygians) went through a remarkable diversification in the beginning of the Triassic, leading to peak diversity during the Middle Triassic; however, the pattern of this diversification is still not well understood due to a taphonomic megabias . The first stem-group teleosts appeared during

384-555: A chain of mountain ranges stretching from Turkey to Malaysia . Pangaea was fractured by widespread faulting and rift basins during the Triassic—especially late in that period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangaea, which separated eastern North America from Morocco , are of Late Triassic age; in the United States , these thick sediments comprise

480-474: A few exposures in the west. During the Triassic peneplains are thought to have formed in what is now Norway and southern Sweden. Remnants of this peneplain can be traced as a tilted summit accordance in the Swedish West Coast . In northern Norway Triassic peneplains may have been buried in sediments to be then re-exposed as coastal plains called strandflats . Dating of illite clay from

576-531: A flux in ceramic masses and glazes, for the production of glass ceramics, crushed as a filter aggregate (air filtration of poison gas) in ABC bunkers , as filter bed material at water treatment facilities, and ground as a soil improvement product. Trap rock has been used to construct buildings and churches: Trinity Church on the Green with trap rock quarried from Eli Whitney 's quarry is a particularly colorful example of

672-471: A long beak-like snout), and Shringasaurus (a horned herbivore which reached a body length of 3–4 metres (9.8–13.1 ft)). One group of archosauromorphs, the archosauriforms , were distinguished by their active predatory lifestyle, with serrated teeth and upright limb postures. Archosauriforms were diverse in the Triassic, including various terrestrial and semiaquatic predators of all shapes and sizes. The large-headed and robust erythrosuchids were among

768-592: A more rapid rate that the basalt layer above it. Mount Toby is also part of such a geologic layer cake. The bottom layer is composed of arkose sandstone, visible across the Connecticut River on Sugarloaf Mountain in Deerfield, Massachusetts . The middle layer is composed basalt ; it is most visible as the geology of the Pocumtuck Ridge , to the northwest of Mount Toby. The top (youngest) layer

864-407: A number of locations. Hunting is permitted in some areas, in season. Much of the trail is also suitable for cross country skiing or backcountry skiing , and some sections are open to mountain biking and horseback riding . Potential trail-use hazards include poison ivy and deer ticks (which are known to carry Lyme disease ). Poisonous snakes are considered extremely rare or extinct along

960-449: A period of 20 million years. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending it a distinct reddish appearance. Huge slopes made of fractured basalt scree , such as the one beneath the cliffs on Bare Mountain, are common. Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows, which eventually lithified into sedimentary rock , such as

1056-617: A pseudosuchian. Pseudosuchians were far more ecologically dominant in the Triassic, including large herbivores (such as aetosaurs ), large carnivores (" rauisuchians "), and the first crocodylomorphs (" sphenosuchians "). Aetosaurs were heavily-armored reptiles that were common during the last 30 million years of the Late Triassic until they died out at the Triassic-Jurassic extinction. Most aetosaurs were herbivorous and fed on low-growing plants, but some may have eaten meat. " rauisuchians " (formally known as paracrocodylomorphs ) were

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1152-674: A red-orange-brown-colored, natural-faced trap rock. Well-known examples of outcropping trap rock include both intrusive sills and extrusive lava flows. They include the Palisades Sill , a Triassic , 200- Ma diabase intrusion that forms the Palisades along 80 kilometers (50 mi) of the Hudson River in New York and New Jersey . Vast areas of trap rock in the form of thick lava flows and other volcanic rocks comprise

1248-458: A short period of time, becoming extinct about 220 million years ago. They were exceptionally abundant in the middle of the Triassic, as the primary large herbivores in many Carnian-age ecosystems. They sheared plants with premaxillary beaks and plates along the upper jaw with multiple rows of teeth. Allokotosaurs were iguana-like reptiles, including Trilophosaurus (a common Late Triassic reptile with three-crowned teeth), Teraterpeton (which had

1344-554: A small suburban development; another passes through a revegetated landfill; and yet another follows a mowed path along railroad tracks. The Robert Frost Trail has undergone periodic extensions to its length. The most recent included routing the trail over the western half of the Holyoke Range; a proposed northern extension would bring the trail to the Deerfield River . Outdated internet and print sources still describe

1440-449: A strandflat of Bømlo , southern Norway, have shown that landscape there became weathered in Late Triassic times ( c. 210 million years ago) with the landscape likely also being shaped during that time. Eustatic sea level in the Triassic was consistently low compared to the other geological periods. The beginning of the Triassic was around present sea level, rising to about 10–20 metres (33–66 ft) above present-day sea level during

1536-585: A supercontinent has less shoreline compared to a series of smaller continents, Triassic marine deposits are relatively uncommon on a global scale. A major exception is in Western Europe , where the Triassic was first studied. The northeastern margin of Gondwana was a stable passive margin along the Neo-Tethys Ocean, and marine sediments have been preserved in parts of northern India and Arabia . In North America , marine deposits are limited to

1632-452: Is 1,300 feet (396 m) from bank to bank at the southern terminus of the Robert Frost Trail and is navigable by power boat. Seasonal spring flooding replenishes the nutrients in the surrounding agricultural land. The Robert Frost Trail, blazed with orange rectangles, is considered easy hiking with occasional rugged sections. It is open to hiking , snowshoeing , picnicking , and other passive activities. Swimming and fishing are possible at

1728-422: Is a popular swimming hole . The Robert Frost Trail passes through land in the following incorporated towns: Hadley , South Hadley , Amherst , Granby , Belchertown , Pelham , Shutesbury , Leverett , Sunderland , Wendell and Montague . The Robert Frost Trail might be divided into three general geo-ecological landscapes. Both the Holyoke Range and Mount Toby were formed 200 million years ago between

1824-468: Is a recent study of North American faunas. In the Petrified Forest of northeast Arizona there is a unique sequence of late Carnian-early Norian terrestrial sediments. An analysis in 2002 found no significant change in the paleoenvironment. Phytosaurs , the most common fossils there, experienced a change-over only at the genus level, and the number of species remained the same. Some aetosaurs ,

1920-564: Is also used to refer to flood (plateau) basalts , such as the Deccan Traps and Siberian Traps . The erosion of trap rock created by the stacking of successive lava flows often creates a distinct stairstep landscape from which the term trap was derived from the Swedish word trappa , which means "stairs". The slow cooling of magma either as a sill or as a thick lava flow sometimes creates systematic vertical fractures within

2016-705: Is composed of Mount Toby Conglomerate. Both Mount Toby and the Holyoke Range are considered among the most biodiverse areas in New England. The trap rock Holyoke Range hosts a combination of microclimates including dry oak savannas , moist ravines dense with eastern hemlock and cooler climate plant species, and talus slopes, rich in nutrients, support a number of calcium-loving plants uncommon in Massachusetts. Fern and orchid species are particularly prolific on Mount Toby; forty-two of forty-five possible native fern species grow there as do rare orchids such as

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2112-534: Is geologically related to the higher White Mountains of New Hampshire, farther to the north. The terrain is rugged with many woodland ledges and ravines. The uplands support transitional forests of species common to both the oak-hickory and northern hardwood forest types. Ravines support significant stands of eastern hemlock . Tree and shrub species also include sugar maple ; red maple ; gray, black, paper, and yellow birch ; white ash ; black oak and red oak ; striped maple and mountain laurel . A third of

2208-508: Is likely a paraphyletic group rather than a true clade. Tanystropheids were a family of protorosaurs which elevated their neck size to extremes, with the largest genus Tanystropheus having a neck longer than its body. The protorosaur family Sharovipterygidae used their elongated hindlimbs for gliding. Other archosauromorphs, such as rhynchosaurs and allokotosaurs , were mostly stocky-bodied herbivores with specialized jaw structures. Rhynchosaurs, barrel-gutted herbivores, thrived for only

2304-469: Is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate , providing a climate suitable for forests and vertebrates, including reptiles. Pangaea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters. The strong contrast between the Pangea supercontinent and

2400-460: Is superimposed by 22 sea level drop events widespread in the geologic record, mostly of minor (less than 25-metre (82 ft)) and medium (25–75-metre (82–246 ft)) magnitudes. A lack of evidence for Triassic continental ice sheets suggest that glacial eustasy is unlikely to be the cause of these changes. The Triassic continental interior climate was generally hot and dry, so that typical deposits are red bed sandstones and evaporites . There

2496-464: Is to picture a layer cake tilted slightly up with some of the frosting (the sedimentary layer) removed in between. A good example of this layer-cake structure can be found on the Robert Frost Trail beneath Mount Norwottuck at the Horse Caves. The summit of Norwottuck is made of basalt; directly beneath the summit are the Horse Caves, a deep overhang where the weaker sedimentary layer has worn away at

2592-409: Is used as ballast for railroad track bed and hydraulic engineering rock ( riprap ) in coast and bank protection for paving embankments. It is also used for the production of cast rock that is used in corrosion and abrasion protection, as for sewage pipes and acid-resistant rocks. Other uses include gardening and landscaping, for the production of millstones, for the production of mineral wool , as

2688-578: The Carnian (early part of the Late Triassic), some advanced cynodonts gave rise to the first mammals . During the Triassic, archosaurs displaced therapsids as the largest and most ecologically prolific terrestrial amniotes. This "Triassic Takeover" may have contributed to the evolution of mammals by forcing the surviving therapsids and their mammaliaform successors to live as small, mainly nocturnal insectivores . Nocturnal life may have forced

2784-482: The Deccan Traps of India and Siberian Traps of Russia. Other prominent basalt ridges, mountains, buttes, canyons, and other landscape features include: Triassic The Triassic ( / t r aɪ ˈ æ s ɪ k / try- ASS -ik ; sometimes symbolized 🝈 ) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya ), to

2880-614: The Jurassic , when the temnospondyls had become very rare. Most of the Reptiliomorpha , stem-amniotes that gave rise to the amniotes, disappeared in the Triassic, but two water-dwelling groups survived: Embolomeri that only survived into the early part of the period, and the Chroniosuchia , which survived until the end of the Triassic. The Permian–Triassic extinction devastated terrestrial life. Biodiversity rebounded as

2976-568: The Lake Lugano region of northern Italy and southern Switzerland , was in Middle Triassic times a lagoon behind reefs with an anoxic bottom layer, so there were no scavengers and little turbulence to disturb fossilization, a situation that can be compared to the better-known Jurassic Solnhofen Limestone lagerstätte . The remains of fish and various marine reptiles (including the common pachypleurosaur Neusticosaurus , and

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3072-632: The Massachusetts Department of Conservation and Recreation , the Five Colleges , and several conservation non-profit organizations. 42°29′16″N 72°32′15″W  /  42.48778°N 72.53750°W  / 42.48778; -72.53750 Trap rock Trap rock , also known as either trapp or trap , is any dark-colored, fine-grained, non-granitic intrusive or extrusive igneous rock . Types of trap rock include basalt , peridotite , diabase , and gabbro . Trap

3168-533: The Mount Orient ledges, Atkins Reservoir, Cushman Brook Ravine, Puffer's Pond, and the Leverett Knobs. The ledges of Mount Orient and the swimming beach at Puffer's Pond are popular locally. Harkness Brook, Amethyst Brook, and Cushman brook offer shaded brookside walking and cascades. Lawrence Swamp is a major local wildlife habitat and aquifer. The northern section of the Robert Frost Trail traverses

3264-658: The Newark Supergroup . Rift basins are also common in South America, Europe, and Africa. Terrestrial environments are particularly well-represented in the South Africa, Russia, central Europe, and the southwest United States. Terrestrial Triassic biostratigraphy is mostly based on terrestrial and freshwater tetrapods, as well as conchostracans ("clam shrimps"), a type of fast-breeding crustacean which lived in lakes and hypersaline environments. Because

3360-474: The Olenekian and Anisian of Gondwana . Both kannemeyeriiform dicynodonts and gomphodont cynodonts remained important herbivores during much of the period. Therocephalians included both large predators ( Moschorhinus ) and herbivorous forms ( bauriids ) until their extinction midway through the period. Ecteniniid cynodonts played a role as large-sized, cursorial predators in the Late Triassic. During

3456-436: The showy lady slipper and the ram's head lady slipper . The Holyoke Range is also an important seasonal raptor migration path. Mount Orient and the section of the Robert Frost Trail north of Mount Toby, from Stoddard Hill to Ruggles Pond, belong to an upland plateau composed of 400 million year old metamorphic rock , mostly schist , gneiss and quartzite . The plateau, averaging 1,000 feet (300 m) above sea level,

3552-735: The surviving species repopulated empty terrain, but these were short-lived. Diverse communities with complex food-web structures took 30 million years to reestablish. Archosauromorph reptiles, which had already appeared and diversified to an extent in the Permian Period, exploded in diversity as an adaptive radiation in response to the Permian-Triassic mass extinction. By the Early Triassic, several major archosauromorph groups had appeared. Long-necked, lizard-like early archosauromorphs were known as protorosaurs , which

3648-463: The temnospondyls , giant aquatic predators that had survived the end-Permian extinction and saw a new burst of diversification in the Triassic, before going extinct by the end; however, early crown-group lissamphibians (including stem-group frogs , salamanders and caecilians ) also became more common during the Triassic and survived the extinction event. The earliest known neopterygian fish, including early holosteans and teleosts , appeared near

3744-524: The thecodonts ) disappeared, as did most of the large labyrinthodont amphibians, groups of small reptiles, and most synapsids. Some of the early, primitive dinosaurs also became extinct, but more adaptive ones survived to evolve into the Jurassic. Surviving plants that went on to dominate the Mesozoic world included modern conifers and cycadeoids. The cause of the Late Triassic extinction is uncertain. It

3840-437: The traversodont cynodonts—were much reduced in the northern half of Pangaea ( Laurasia ). These extinctions within the Triassic and at its end allowed the dinosaurs to expand into many niches that had become unoccupied. Dinosaurs became increasingly dominant, abundant and diverse, and remained that way for the next 150 million years. The true "Age of Dinosaurs" is during the following Jurassic and Cretaceous periods, rather than

3936-832: The Anisian to Ladinian of the Tethysian domain, and from the Carnian and Rhaetian of a larger area that includes also the Boreal domain (e.g., Svalbard Islands), the North American continent, the South China block and Argentina . The best-studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event . The Early Triassic was the hottest portion of

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4032-405: The Carnian and include early sauropodomorphs and theropods. Most Triassic dinosaurs were small predators and only a few were common, such as Coelophysis , which was 1 to 2 metres (3.3 to 6.6 ft) long. Triassic sauropodomorphs primarily inhabited cooler regions of the world. The large predator Smok was most likely also an archosaur, but it is uncertain if it was a primitive dinosaur or

4128-563: The Early Triassic, forming small patches of reefs of modest extent compared to the great reef systems of Devonian or modern times. At the end of the Carnian, a reef crisis occurred in South China. Serpulids appeared in the Middle Triassic. Microconchids were abundant. The shelled cephalopods called ammonites recovered, diversifying from a single line that survived the Permian extinction. Bivalves began to rapidly diversify during

4224-402: The Early Triassic, while others (e.g. capitosaurs ) remained successful throughout the whole period, or only came to prominence in the Late Triassic (e.g. Plagiosaurus , metoposaurs ). The first Lissamphibians (modern amphibians) appear in the Triassic, with the progenitors of the first frogs already present by the Early Triassic. However, the group as a whole did not become common until

4320-562: The Early and Middle Triassic. Sea level rise accelerated in the Ladinian, culminating with a sea level up to 50 metres (164 ft) above present-day levels during the Carnian. Sea level began to decline in the Norian, reaching a low of 50 metres (164 ft) below present sea level during the mid-Rhaetian. Low global sea levels persisted into the earliest Jurassic. The long-term sea level trend

4416-619: The Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate the Mesozoic Era. Reptiles , especially archosaurs , were the chief terrestrial vertebrates during this time. A specialized group of archosaurs, called dinosaurs , first appeared in

4512-613: The Jurassic. There were many types of marine reptiles. These included the Sauropterygia , which featured pachypleurosaurus and nothosaurs (both common during the Middle Triassic, especially in the Tethys region), placodonts , the earliest known herbivorous marine reptile Atopodentatus , and the first plesiosaurs . The first of the lizardlike Thalattosauria ( askeptosaurs ) and the highly successful ichthyopterygians , which appeared in Early Triassic seas, soon diversified. By

4608-432: The Late Triassic but did not become dominant until the succeeding Jurassic Period. Archosaurs that became dominant in this period were primarily pseudosuchians , relatives and ancestors of modern crocodilians , while some archosaurs specialized in flight, the first time among vertebrates, becoming the pterosaurs . Therapsids , the dominant vertebrates of the preceding Permian period, saw a brief surge in diversification in

4704-600: The Latest Olenekian Cooling (LOC), from 248 to 247 Ma, temperatures cooled by about 6 °C. The Middle Triassic was cooler than the Early Triassic, with temperatures falling over most of the Anisian, with the exception of a warming spike in the latter portion of the stage. From 242 to 233 Ma, the Ladinian-Carnian Cooling (LCC) ensued. At the beginning of the Carnian, global temperatures continued to be relatively cool. The eruption of

4800-486: The Middle Triassic, becoming highly abundant in the oceans. Aquatic insects rapidly diversified during the Middle Triassic, with this time interval representing a crucial diversification for Holometabola , the clade containing the majority of modern insect species. In the wake of the Permian-Triassic mass extinction event , the fish fauna was remarkably uniform, with many families and genera exhibiting

4896-618: The Middle Triassic, some ichthyopterygians were achieving very large body masses. Among other reptiles, the earliest turtles , like Proganochelys and Proterochersis , appeared during the Norian Age (Stage) of the Late Triassic Period. The Lepidosauromorpha , specifically the Sphenodontia , are first found in the fossil record of the earlier Carnian Age, though the earliest lepidosauromorphs likely occurred in

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4992-450: The Permian extinction, Archaeplastida (red and green algae) had been the major marine phytoplanktons since about 659–645 million years ago, when they replaced marine planktonic cyanobacteria , which first appeared about 800 million years ago, as the dominant phytoplankton in the oceans. In the Triassic, secondary endosymbiotic algae became the most important plankton. In marine environments , new modern types of corals appeared in

5088-475: The Permian. The Procolophonidae , the last surviving parareptiles , were an important group of small lizard-like herbivores. The drepanosaurs were a clade of unusual, chameleon-like arboreal reptiles with birdlike heads and specialised claws. Three therapsid groups survived into the Triassic: dicynodonts , therocephalians , and cynodonts . The cynodont Cynognathus was a characteristic top predator in

5184-672: The Robert Frost Trail is located within the bottomlands of the Connecticut River Valley, a relatively flat landscape with occasional rounded hills. The underlying strata is sedimentary rock, and the area has a long history of successful agriculture dating back to pre-colonial times. Soils are rich enough to support a commercial tobacco crop. The area is characterized by wetlands, meandering brooks with deeply cut banks, agricultural land, and patches of northern riverine forest and red maple swamp. Tree species include willow , American elm , and sycamore . The Connecticut River

5280-405: The Robert Frost Trail on Mount Toby, plunges 100 feet (30 m) over ledges in a series of pools, chutes, and cataracts. Cranberry Pond, a glacial kettle pond , is popular for non-motorized boating and ice skating. The Pigpen is a 20 feet (6.1 m) wide by 15 feet (4.6 m) high natural rock enclosure overshadowed by steep ledges, while Ruggles Pond, the centerpiece of Wendell State Forest,

5376-600: The Robert Frost Trail. Although the trail environs are black bear habitat, problem encounters with bears are rare. Guides, maps, and trail descriptions are available from a variety of sources, most notably the town of Amherst Conservation Department, and the Appalachian Mountain Club . Publications are available for purchase at the Amherst town hall and at local bookstores and hiking outfitters. However, most trail maps are out of date. Published in 2004,

5472-408: The Triassic (teleosts are by far the most diverse group of fish today). Predatory actinopterygians such as saurichthyids and birgeriids , some of which grew over 1.2 m (3.9 ft) in length, appeared in the Early Triassic and became widespread and successful during the period as a whole. Lakes and rivers were populated by lungfish (Dipnoi), such as Ceratodus , which are mainly known from

5568-476: The Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event , that wiped out many groups, including most pseudosuchians, and allowed dinosaurs to assume dominance in the Jurassic. The Triassic

5664-609: The Triassic, enlarging the Neo-Tethys Ocean which formed in their wake. At the same time, they forced the Paleo-Tethys Ocean to shrink as it was being subducted under Asia. By the end of the Triassic, the Paleo-Tethys Ocean occupied a small area and the Cimmerian terranes began to collide with southern Asia. This collision, known as the Cimmerian Orogeny , continued into the Jurassic and Cretaceous to produce

5760-428: The Triassic, with dicynodonts and cynodonts quickly becoming dominant, but they declined throughout the period with the majority becoming extinct by the end. However, the first stem-group mammals ( mammaliamorphs ), themselves a specialized subgroup of cynodonts, appeared during the Triassic and would survive the extinction event, allowing them to radiate during the Jurassic. Amphibians were primarily represented by

5856-839: The Wrangellia Large Igneous Province around 234 Ma caused abrupt global warming, terminating the cooling trend of the LCC. This warming was responsible for the Carnian Pluvial Event and resulted in an episode of widespread global humidity. The CPE ushered in the Mid-Carnian Warm Interval (MCWI), which lasted from 234 to 227 Ma. At the Carnian-Norian boundary occurred a positive δ C excursion believed to signify an increase in organic carbon burial. From 227 to 217 Ma, there

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5952-690: The beginning of the Jurassic Period 201.4 Mya. The Triassic is the first and shortest period of the Mesozoic Era and the seventh period of the Phanerozoic Eon . Both the start and end of the period are marked by major extinction events . The Triassic Period is subdivided into three epochs: Early Triassic , Middle Triassic and Late Triassic . The Triassic began in the wake of the Permian–Triassic extinction event , which left

6048-415: The beginning of the Triassic, and quickly diversified to become among the dominant groups of fish in both freshwater and marine habitats. The vast supercontinent of Pangaea dominated the globe during the Triassic, but in the latest Triassic ( Rhaetian ) and Early Jurassic it began to gradually rift into two separate landmasses: Laurasia to the north and Gondwana to the south. The global climate during

6144-455: The bizarre long-necked archosauromorph Tanystropheus ), along with some terrestrial forms like Ticinosuchus and Macrocnemus , have been recovered from this locality. All these fossils date from the Anisian and Ladinian ages (about 242 Ma ago). The Triassic Period ended with a mass extinction, which was particularly severe in the oceans; the conodonts disappeared, as did all

6240-410: The conglomerate rock Mount Toby is composed of. The resulting "layer cake" of basalt and sedimentary sheets eventually faulted and tilted upward. Subsequent erosion wore away the weaker sedimentary layers a faster rate than the basalt layers, leaving the abruptly tilted edges of the basalt sheets exposed, creating the distinct linear ridge and dramatic cliff faces visible today. One way to imagine this

6336-412: The corresponding rocks are referred to as Lower, Middle, or Upper Triassic. The faunal stages from the youngest to oldest are: During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent , Pangaea ( lit.   ' entire land ' ). This supercontinent was more-or-less centered on the equator and extended between the poles, though it did drift northwards as

6432-506: The dental plates, abundant in the fossils record. Hybodonts , a group of shark-like cartilaginous fish , were dominant in both freshwater and marine environments throughout the Triassic. Last survivors of the mainly Palaeozoic Eugeneodontida are known from the Early Triassic. Temnospondyl amphibians were among those groups that survived the Permian–Triassic extinction. Once abundant in both terrestrial and aquatic environments,

6528-428: The dominant carnivores in the early Triassic. Phytosaurs were a particularly common group which prospered during the Late Triassic. These long-snouted and semiaquatic predators resemble living crocodiles and probably had a similar lifestyle, hunting for fish and small reptiles around the water's edge. However, this resemblance is only superficial and is a prime-case of convergent evolution. True archosaurs appeared in

6624-405: The early Triassic, splitting into two branches: Avemetatarsalia (the ancestors to birds) and Pseudosuchia (the ancestors to crocodilians). Avemetatarsalians were a minor component of their ecosystems, but eventually produced the earliest pterosaurs and dinosaurs in the Late Triassic. Early long-tailed pterosaurs appeared in the Norian and quickly spread worldwide. Triassic dinosaurs evolved in

6720-557: The end of the Triassic period and the beginning of the Jurassic . The Holyoke Range, part of the Metacomet Ridge that extends 100 miles (160 km) south to Long Island Sound , are composed of basalt , an extrusive volcanic rock . This basalt ridge is the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa over

6816-640: The entire Phanerozoic, seeing as it occurred during and immediately after the discharge of titanic volumes of greenhouse gases from the Siberian Traps. The Early Triassic began with the Permian-Triassic Thermal Maximum (PTTM) and was followed by the brief Dienerian Cooling (DC) from 251 to 249 Ma, which was in turn followed by the Latest Smithian Thermal Maximum (LSTT) around 249 to 248 Ma. During

6912-480: The extinct family Cheirolepidiaceae , which first appeared in the Late Triassic, and would be prominent throughout most of the rest of the Mesozoic. No known coal deposits date from the start of the Triassic Period. This is known as the Early Triassic "coal gap" and can be seen as part of the Permian–Triassic extinction event . Possible explanations for the coal gap include sharp drops in sea level at

7008-466: The fare. Also located on this trail section are the Horse Caves, an overhang of sedimentary rock said to have been used as a bivouac by rebels during Shays' Rebellion . The middle section of the Robert Frost Trail traverses the Connecticut River Valley in the vicinity of eastern Amherst , south Leverett , and abutting towns. Highlights along the way include the 1,000-acre (4.0 km) Lawrence Swamp, Pomroy Pond, Harkness Brook Ravine, Amethyst Brook,

7104-521: The global ocean triggered intense cross-equatorial monsoons , sometimes referred to as the Pangean megamonsoons . The Triassic may have mostly been a dry period, but evidence exists that it was punctuated by several episodes of increased rainfall in tropical and subtropical latitudes of the Tethys Sea and its surrounding land. Sediments and fossils suggestive of a more humid climate are known from

7200-420: The impact. So, the evidence suggests the Manicouagan impact preceded the end of the Triassic by approximately 10±2 Ma. It could not therefore be the immediate cause of the observed mass extinction. The number of Late Triassic extinctions is disputed. Some studies suggest that there are at least two periods of extinction towards the end of the Triassic, separated by 12 to 17 million years. But arguing against this

7296-401: The keystone predators of most Triassic terrestrial ecosystems. Over 25 species have been found, including giant quadrupedal hunters, sleek bipedal omnivores, and lumbering beasts with deep sails on their backs. They probably occupied the large-predator niche later filled by theropods. "Rauisuchians" were ancestral to small, lightly-built crocodylomorphs, the only pseudosuchians which survived into

7392-545: The mammaliaforms to develop fur and a higher metabolic rate . Two Early Triassic lagerstätten (high-quality fossil beds), the Dienerian aged Guiyang biota and the earliest Spathian aged Paris biota stand out due to their exceptional preservation and diversity . They represent the earliest lagerstätten of the Mesozoic era and provide insight into the biotic recovery from the Permian-Triassic mass extinction event. The Monte San Giorgio lagerstätte, now in

7488-453: The marine reptiles except ichthyosaurs and plesiosaurs . Invertebrates like brachiopods and molluscs (such as gastropods ) were severely affected. In the oceans, 22% of marine families and possibly about half of marine genera went missing. Though the end-Triassic extinction event was not equally devastating in all terrestrial ecosystems, several important clades of crurotarsans (large archosaurian reptiles previously grouped together as

7584-458: The modern Pacific Ocean . Practically all deep-ocean crust present during the Triassic has been recycled through the subduction of oceanic plates, so very little is known about the open ocean from this time period. Most information on Panthalassan geology and marine life is derived from island arcs and rare seafloor sediments accreted onto surrounding land masses, such as present-day Japan and western North America. The eastern edge of Pangea

7680-430: The next most common tetrapods, and early dinosaurs, passed through unchanged. However, both phytosaurs and aetosaurs were among the groups of archosaur reptiles completely wiped out by the end-Triassic extinction event. It seems likely then that there was some sort of end-Carnian extinction, when several herbivorous archosauromorph groups died out, while the large herbivorous therapsids —the kannemeyeriid dicynodonts and

7776-467: The northern slopes of the range from Mount Holyoke to Taylor Notch, along the ridge line, descending south to Lithia Springs Reservoir, before climbing again to the ridgeline, where it goes north of Mount Hitchcock and Bare Mountain , then crosses to the north slope of the range before summiting Rattlesnake Knob (the eastern peak of Mount Norwottuck ), and Long Mountain. Microclimate ecosystems, rare plant habitats, vernal pools, caves, and abrupt cliffs are

7872-438: The official trail guide only mentions the west Holyoke range section of the trail to be in development. Other online resources acknowledge that the trail guide is out of date, but fail to provide updated information on this new section. A patchwork of state land, town land, and privately owned land, the Robert Frost Trail is managed and maintained by a local cooperative effort. Partners include town governments, private landowners,

7968-402: The order Isoetales (which contains living quillworts ), rose to prominence due to the environmental instability following the Permian-Triassic extinction, with one particularly notable example being the genus Pleuromeia , which grew in columnar like fashion, sometimes reaching a height of 2 metres (6.6 ft). The relevance of lycophytes declined from the Middle Triassic onwards, following

8064-504: The period progressed. Southern Pangea, also known as Gondwana , was made up by closely-appressed cratons corresponding to modern South America , Africa , Madagascar , India , Antarctica , and Australia . North Pangea, also known as Laurussia or Laurasia , corresponds to modern-day North America and the fragmented predecessors of Eurasia . The western edge of Pangea lay at the margin of an enormous ocean, Panthalassa ( lit.   ' entire sea ' ), which roughly corresponds to

8160-482: The resulting layer of trap rock. These fractures often form rock columns that are typically hexagonal, but also four- to eight-sided. Trap rock, i.e. basalt or diabase, has a variety of uses. A major use for basalt is crushed rock for road and housing construction in concrete , macadam , and paving stones. Because of its insensitivity to chemical influences, resistance to mechanical stress, high dry relative density, frost resistance, and seawater resistance, trap rock

8256-487: The return of more stable environmental conditions. While having first appeared during the Permian, the extinct seed plant group Bennettitales first became a prominent element in global floras during the Late Triassic, a position they would hold for much of the Mesozoic. In the Southern Hemisphere landmasses of Gondwana, the tree Dicroidium , an extinct " seed fern " belong to the order Corystospermales

8352-648: The summit of Mount Toby , Stoddard Hill, and Dry Hill. Features along the route include the Mount Toby firetower, Cranberry Pond, the Pigpen, a historic sawmill and dam, and Ruggles Pond in Wendell State Forest. Mount Toby , regarded as one of the most biologically diverse locations in New England, is a conglomerate rock massif unique in Massachusetts. The firetower on its summit provides panoramic views. Roaring Falls, located 0.25 miles (400 m) off

8448-676: The terminus of the Triassic, there was an extreme warming event referred to as the End-Triassic Thermal Event (ETTE), which was responsible for the Triassic-Jurassic mass extinction. Bubbles of carbon dioxide in basaltic rocks dating back to the end of the Triassic indicate that volcanic activity from the Central Atlantic Magmatic Province helped trigger climate change in the ETTE. During the Early Triassic, lycophytes , particularly those of

8544-595: The terrestrial species had mostly died out during the extinction event. The Triassic survivors were aquatic or semi-aquatic, and were represented by Tupilakosaurus , Thabanchuia , Branchiosauridae and Micropholis , all of which died out in Early Triassic, and the successful Stereospondyli , with survivors into the Cretaceous Period. The largest Triassic stereospondyls, such as Mastodonsaurus , were up to 4 to 6 metres (13 to 20 ft) in length. Some lineages (e.g. trematosaurs ) flourished briefly in

8640-577: The time of the Permo-Triassic boundary; acid rain from the Siberian Traps eruptions or from an impact event that overwhelmed acidic swamps; climate shift to a greenhouse climate that was too hot and dry for peat accumulation; evolution of fungi or herbivores that were more destructive of wetlands; the extinction of all plants adapted to peat swamps, with a hiatus of several million years before new plant species evolved that were adapted to peat swamps; or soil anoxia as oxygen levels plummeted. Before

8736-515: The trail as either 33 or 40 miles (53 or 64 km) long. The 110-mile (180 km) Metacomet-Monadnock Trail intersects the Robert Frost Trail several times, as do a lengthy network of smaller trails (many managed by the Amherst Department of Conservation), allowing for a variety of loop-hike possibilities. The southernmost section of the Robert Frost Trail weaves over and around the trap rock Holyoke Range several times. It follows

8832-615: Was a dominant element in forest habitats across the region during the Middle-Late Triassic. During the Late Triassic, the Ginkgoales (which today are represented by only a single species, Ginkgo biloba ) underwent considerable diversification. Conifers were abundant during the Triassic, and included the Voltziales (which contains various lineages, probably including those ancestral to modern conifers), as well as

8928-673: Was a relatively cool period known as the Early Norian Cool Interval (ENCI), after which occurred the Mid-Norian Warm Interval (MNWI) from 217 to 209 Ma. The MNWI was briefly interrupted around 214 Ma by a cooling possibly related to the Manicouagan impact . Around 212 Ma, a 10 Myr eccentricity maximum caused a paludification of Pangaea and a reduction in the size of arid climatic zones. The Rhaetian Cool Interval (RCI) lasted from 209 to 201 Ma. At

9024-505: Was accompanied by huge volcanic eruptions that occurred as the supercontinent Pangaea began to break apart about 202 to 191 million years ago (40Ar/39Ar dates), forming the Central Atlantic Magmatic Province (CAMP), one of the largest known inland volcanic events since the planet had first cooled and stabilized. Other possible but less likely causes for the extinction events include global cooling or even

9120-484: Was encroached upon by a pair of extensive oceanic basins: The Neo-Tethys (or simply Tethys) and Paleo-Tethys Oceans . These extended from China to Iberia, hosting abundant marine life along their shallow tropical peripheries. They were divided from each other by a long string of microcontinents known as the Cimmerian terranes . Cimmerian crust had detached from Gondwana in the early Permian and drifted northwards during

9216-451: Was named in 1834 by Friedrich August von Alberti , after a succession of three distinct rock layers (Greek triás meaning 'triad') that are widespread in southern Germany : the lower Buntsandstein (colourful sandstone ) , the middle Muschelkalk (shell-bearing limestone ) and the upper Keuper (coloured clay ). On the geologic time scale , the Triassic is usually divided into Early , Middle , and Late Triassic Epochs , and

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