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76-700: The Bering Land Bridge National Preserve is one of the most remote Protected areas of the United States , located on the Seward Peninsula . The National Preserve protects a remnant of the Bering Land Bridge that connected Asia with North America more than 13,000 years ago during the Pleistocene ice age . The majority of this land bridge now lies beneath the waters of the Chukchi and Bering Seas . During

152-423: A mantle wedge above the descending slab. The slab releases water vapor and other volatiles as it descends, which further lowers the melting point, further increasing the amount of decompression melting. Each tectonic setting produces basalt with its own distinctive characteristics. The mineralogy of basalt is characterized by a preponderance of calcic plagioclase feldspar and pyroxene . Olivine can also be

228-493: A basalt is diagnostic of how and where it erupted—for example, whether into the sea, in an explosive cinder eruption or as creeping pāhoehoe lava flows, the classic image of Hawaiian basalt eruptions. Basalt that erupts under open air (that is, subaerially ) forms three distinct types of lava or volcanic deposits: scoria ; ash or cinder ( breccia ); and lava flows. Basalt in the tops of subaerial lava flows and cinder cones will often be highly vesiculated , imparting

304-574: A bay in the Kotzebue Sound , when it was surprised by a combination of a tidal surge and flooding in connection with a winter storm. When the tidal surge reached the herd, it broke the ice underneath it and the herd plunged into the icy water. The temperature was below –30 °C, and the whole herd was killed and frozen in the ice. Four of the animals had been fitted with radio collars, and they were found by researchers looking for their signals. In addition to their reintroduction to this national preserve,

380-463: A bunkhouse was dragged in by Alaska Road Commission workers in 1949. In 1953, the nearby village of Shishmaref received $ 53,000 in state funds to construct a public bath house. It is possible that the springs were used traditionally by Inupiat residents for cooking, for healing and spiritual purposes. Anthropologists who studied the Inupiat in the area reported local beliefs that the healing influences at

456-442: A distinctive pillow shape, through which the hot lava breaks to form another pillow. This "pillow" texture is very common in underwater basaltic flows and is diagnostic of an underwater eruption environment when found in ancient rocks. Pillows typically consist of a fine-grained core with a glassy crust and have radial jointing. The size of individual pillows varies from 10 cm up to several metres. When pāhoehoe lava enters

532-529: A dog team and Inupiat assistants, was probably the first white man to reach the hot springs in May, 1900. McLennan may have staked a mining claim nearby but left the country by September, 1901. Another miner, John Sirene, built a cabin and maintained a garden at the springs. Miners used the area intermittently until around 1915, when prospectors built a cabin, bathhouse, and a bathing pool that was 10 to 12 feet in diameter nearby. A runway may have been constructed in 1923 and

608-427: A flow can shrink in the vertical dimension without fracturing, it cannot easily accommodate shrinking in the horizontal direction unless cracks form; the extensive fracture network that develops results in the formation of columns . These structures, or basalt prisms , are predominantly hexagonal in cross-section, but polygons with three to twelve or more sides can be observed. The size of the columns depends loosely on

684-465: A high content of plagioclase; these are sometimes described as leucobasalts . It can be difficult to distinguish between lighter-colored basalt and andesite , so field researchers commonly use a rule of thumb for this purpose, classifying it as basalt if it has a color index of 35 or greater. The physical properties of basalt result from its relatively low silica content and typically high iron and magnesium content. The average density of basalt

760-621: A lightweight "frothy" texture to the rock. Basaltic cinders are often red, coloured by oxidized iron from weathered iron-rich minerals such as pyroxene . ʻAʻā types of blocky cinder and breccia flows of thick, viscous basaltic lava are common in Hawaiʻi. Pāhoehoe is a highly fluid, hot form of basalt which tends to form thin aprons of molten lava which fill up hollows and sometimes forms lava lakes . Lava tubes are common features of pāhoehoe eruptions. Basaltic tuff or pyroclastic rocks are less common than basaltic lava flows. Usually basalt

836-458: A listing on the National Register of Historic Places or a designation as a National Historic Landmark . States and local zoning bodies may or may not choose to protect these. The state of Colorado , for example, is very clear that it does not set any limits on owners of NRHP properties. Federal protected area designations International protected area designations Every state has

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912-623: A lower total content of alkali oxides than trachybasalt and most basanites and tephrites. Basalt generally has a composition of 45–52 wt% SiO 2 , 2–5 wt% total alkalis, 0.5–2.0 wt% TiO 2 , 5–14 wt% FeO and 14 wt% or more Al 2 O 3 . Contents of CaO are commonly near 10 wt%, those of MgO commonly in the range 5 to 12 wt%. High-alumina basalts have aluminium contents of 17–19 wt% Al 2 O 3 ; boninites have magnesium (MgO) contents of up to 15 percent. Rare feldspathoid -rich mafic rocks, akin to alkali basalts, may have Na 2 O + K 2 O contents of 12% or more. The abundances of

988-507: A phenocryst, and when present, may have rims of pigeonite. The groundmass contains interstitial quartz or tridymite or cristobalite . Olivine tholeiitic basalt has augite and orthopyroxene or pigeonite with abundant olivine, but olivine may have rims of pyroxene and is unlikely to be present in the groundmass . Alkali basalts typically have mineral assemblages that lack orthopyroxene but contain olivine. Feldspar phenocrysts typically are labradorite to andesine in composition. Augite

1064-527: A popular destination for tourists. The preserve lies on the northern side of the Seward Peninsula , with 2,697,391 acres (1,091,595 ha). The preserve extends along the coast from a point to the west of Deering along Goodhope Bay to Cape Espenberg , then westward along the shore of the Chukchi Sea . The boundary moves inland to avoid the village of Shishmaref and the Shishmaref Inlet , then rejoins

1140-523: A significant constituent. Accessory minerals present in relatively minor amounts include iron oxides and iron-titanium oxides, such as magnetite , ulvöspinel , and ilmenite . Because of the presence of such oxide minerals, basalt can acquire strong magnetic signatures as it cools, and paleomagnetic studies have made extensive use of basalt. In tholeiitic basalt , pyroxene ( augite and orthopyroxene or pigeonite ) and calcium -rich plagioclase are common phenocryst minerals. Olivine may also be

1216-401: A system of state parks as well as many other types of protected areas (forests, reserves, refuges, recreation areas, etc.). State parks vary widely from urban parks to very large parks that are on a par with national parks. Some state parks, like Adirondack Park , are similar to the national parks of England and Wales , with numerous towns inside the borders of the park. About half the area of

1292-630: A wide variety of local public parks and other protected areas. Some of these are little more than picnic areas or playgrounds ; however, others are extensive nature reserves . South Mountain Park in Phoenix, Arizona , for example, is called the largest city park in the United States; it spans 25 sq mi (65 km ) and contains 58 mi (93 km) of trails. Basalt Basalt ( UK : / ˈ b æ s ɔː l t , - əl t / ; US : / b ə ˈ s ɔː l t , ˈ b eɪ s ɔː l t / )

1368-414: Is Mount Boyan on the south border. There are no roads into the preserve. Access to the preserve is by bush planes or boats during summer months and by ski planes, snowmobiles or dog sleds during the winter. Bering Land Bridge National Preserve contains several sites of geological and prehistorical significance. Serpentine Hot Springs is the preserve's most visited location. Other notable locations in

1444-427: Is 2.9 g/cm , compared, for example, to granite ’s typical density of 2.7 g/cm . The viscosity of basaltic magma is relatively low—around 10 to 10 cP —similar to the viscosity of ketchup , but that is still several orders of magnitude higher than the viscosity of water, which is about 1 cP). Basalt is often porphyritic , containing larger crystals ( phenocrysts ) that formed before the extrusion event that brought

1520-401: Is also produced by some subglacial volcanic eruptions. Basalt is the most common volcanic rock type on Earth, making up over 90% of all volcanic rock on the planet. The crustal portions of oceanic tectonic plates are composed predominantly of basalt, produced from upwelling mantle below the ocean ridges . Basalt is also the principal volcanic rock in many oceanic islands , including

1596-417: Is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low- viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon . More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro . The eruption of basalt lava

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1672-753: Is considered a key to understanding plate tectonics , its compositions have been much studied. Although MORB compositions are distinctive relative to average compositions of basalts erupted in other environments, they are not uniform. For instance, compositions change with position along the Mid-Atlantic Ridge , and the compositions also define different ranges in different ocean basins. Mid-ocean ridge basalts have been subdivided into varieties such as normal (NMORB) and those slightly more enriched in incompatible elements (EMORB). Isotope ratios of elements such as strontium , neodymium , lead , hafnium , and osmium in basalts have been much studied to learn about

1748-478: Is defined as volcanic rock with a content of between 45% and 52% silica and no more than 5% alkali metal oxides. This places basalt in the B field of the TAS diagram. Such a composition is described as mafic . Basalt is usually dark grey to black in colour, due to a high content of augite or other dark-coloured pyroxene minerals, but can exhibit a wide range of shading. Some basalts are quite light-coloured due to

1824-540: Is estimated to be only 1,000 to 2,000 years old, produced from around 75 vents. The largest vent is the Lost Jim Cone, about 75 feet (23 m) high. One remnant of volcanism is the presence of hot springs. The Serpentine Hot Springs produce water at a temperature of 140 °F (60 °C) to 170 °F (77 °C), and have been used for millennia by local people. Granite tors are another volcanic remnant, formed underground and exposed by erosion. Bering Land Bridge has

1900-764: Is located in the Bering Land Bridge National Preserve. The springs are also referred to as Iyat, the Inupiaq word for cooking pot. Serpentine Hot Springs is on the northern part of the Seward Peninsula at 65°51′N, 164°43′W. The springs are situated on the right bank of Hot Springs Creek which flows to the Serpentine River, 47 miles NW of Imuruk Lake . Serpentine Hot Springs was originally described by Arthur J. Collier in U.S. Geological Survey Bulletin (1902). Collier noted that Charles McLennan, who with

1976-550: Is moderated by the coastal location, but temperatures can reach −65 °F (−54 °C) in winter and typical low temperatures in winter are −10 °F (−23 °C) to −20 °F (−29 °C). Summer temperatures average about 50 °F (10 °C). The average annual temperature is 21 °F (−6 °C). An entire herd of 55 muskoxen died in a storm surge in the National Reserve in February 2011. The herd had been crossing

2052-747: Is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System . For example, the bulk of the plains of Venus , which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows ; and basalt is a common rock on the surface of Mars . Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flows that can spread over great areas before cooling and solidifying. Flood basalts are thick sequences of many such flows that can cover hundreds of thousands of square kilometres and constitute

2128-579: Is rich in titanium compared to augite in tholeiitic basalt. Minerals such as alkali feldspar , leucite , nepheline , sodalite , phlogopite mica, and apatite may be present in the groundmass. Basalt has high liquidus and solidus temperatures—values at the Earth's surface are near or above 1200 °C (liquidus) and near or below 1000 °C (solidus); these values are higher than those of other common igneous rocks. The majority of tholeiitic basalts are formed at approximately 50–100 km depth within

2204-402: Is suppressed. Above this depth, submarine eruptions are often explosive, tending to produce pyroclastic rock rather than basalt flows. These eruptions, described as Surtseyan, are characterised by large quantities of steam and gas and the creation of large amounts of pumice . When basalt erupts underwater or flows into the sea, contact with the water quenches the surface and the lava forms

2280-440: Is too hot and fluid to build up sufficient pressure to form explosive lava eruptions but occasionally this will happen by trapping of the lava within the volcanic throat and buildup of volcanic gases . Hawaiʻi's Mauna Loa volcano erupted in this way in the 19th century, as did Mount Tarawera , New Zealand in its violent 1886 eruption. Maar volcanoes are typical of small basalt tuffs, formed by explosive eruption of basalt through

2356-455: Is ultimately derived from Late Latin basaltes , a misspelling of Latin basanites "very hard stone", which was imported from Ancient Greek βασανίτης ( basanites ), from βάσανος ( basanos , " touchstone "). The modern petrological term basalt , describing a particular composition of lava -derived rock, became standard because of its use by Georgius Agricola in 1546, in his work De Natura Fossilium . Agricola applied

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2432-1171: The Antiquities Act . Carter took the action after the Alaska National Interest Lands Conservation Act (ANILCA) was held up in Congress. In 1980 ANILCA was passed, and was signed into law by Carter on 2 December 1980, converting the monument into a national preserve . The preserve's headquarters are in the Sitnasuak Building in Nome . Protected areas of the United States Federal protected areas include lands and waters owned outright ("Fee ownerships"), as well as areas that are secured by easements, leases, etc. In addition to ownership-defined areas, there are numerous overlaying policy designations that apply management protections and use conditions on all or some of individual protected areas (e.g., Wilderness Areas, National Monuments, etc.). As of 2007 , according to

2508-529: The Clementine mission demonstrate that the lunar maria possess a continuum of titanium concentrations, and that the highest concentrations are the least abundant. Lunar basalts show exotic textures and mineralogy, particularly shock metamorphism , lack of the oxidation typical of terrestrial basalts, and a complete lack of hydration . Most of the Moon 's basalts erupted between about 3 and 3.5 billion years ago, but

2584-1176: The Paraná Traps in Brazil, the Siberian Traps in Russia , the Karoo flood basalt province in South Africa, and the Columbia River Plateau of Washington and Oregon . Basalt is also prevalent across extensive regions of the Eastern Galilee , Golan , and Bashan in Israel and Syria . Basalt also is common around volcanic arcs, specially those on thin crust . Ancient Precambrian basalts are usually only found in fold and thrust belts, and are often heavily metamorphosed. These are known as greenstone belts , because low-grade metamorphism of basalt produces chlorite , actinolite , epidote and other green minerals. As well as forming large parts of

2660-671: The United Nations Environment Programme , the U.S. had a total of 6,770 terrestrial nationally designated (federal) protected areas. Federal level protected areas are managed by a variety of agencies, most of which are a part of the National Park Service , a bureau of the United States Department of the Interior . They are often considered the crown jewels of the protected areas. Other areas are managed by

2736-789: The United States Forest Service , the Bureau of Land Management and the United States Fish and Wildlife Service . The United States Army Corps of Engineers is claimed to provide 30 percent of the recreational opportunities on federal lands, mainly through lakes and waterways that they manage. The highest levels of protection, as described by the International Union for Conservation of Nature (IUCN), are Level I (Strict Nature Reserves & Wilderness Areas) and Level II (National Parks). The United States maintains 12 percent of

2812-520: The hypabyssal and plutonic equivalents of basalt. During the Hadean , Archean , and early Proterozoic eons of Earth's history, the chemistry of erupted magmas was significantly different from what it is today, due to immature crustal and asthenosphere differentiation. The resulting ultramafic volcanic rocks, with silica (SiO 2 ) contents below 45% and high magnesium oxide (MgO) content, are usually classified as komatiites . The word "basalt"

2888-524: The lanthanide or rare-earth elements (REE) can be a useful diagnostic tool to help explain the history of mineral crystallisation as the melt cooled. In particular, the relative abundance of europium compared to the other REE is often markedly higher or lower, and called the europium anomaly . It arises because Eu can substitute for Ca in plagioclase feldspar, unlike any of the other lanthanides, which tend to only form cations . Mid-ocean ridge basalts (MORB) and their intrusive equivalents, gabbros, are

2964-463: The Birnirk, Western Thule and Kotzebue Period cultures. This series of cultures spanned the period from 600 AD to the early 1800s, when traditional lifestyles were disrupted by the arrival of Europeans in the area. The fur trade, whaling and missionary activities changed the local economy, which was further altered in the late 19th century by the arrival of prospectors looking for gold on the southern side of

3040-457: The Earth's crust, basalt also occurs in other parts of the Solar System. Basalt commonly erupts on Io (the third largest moon of Jupiter ), and has also formed on the Moon , Mars , Venus , and the asteroid Vesta . The dark areas visible on Earth's moon , the lunar maria , are plains of flood basaltic lava flows. These rocks were sampled both by the crewed American Apollo program and

3116-634: The Level I and II lands in the world. These lands had a total area of 210,000 sq mi (540,000 km ). Because U.S. federal protected areas include both ownership based names, and names related to overlaying policy designations, the naming system for U.S. protected areas results in some types being used by more than one agency. For instance, both the National Park Service and the U.S. Forest Service manage areas designated National Preserves and National Recreation Areas . The National Park Service,

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3192-504: The Seward Peninsula. Prospectors spread out across the peninsula, with hydraulic mining undertaken in the Pinnel River in the preserve. The Seward Peninsula saw a further influx of outsiders during World War II, since Alaska was an important theater of the Pacific war. Bering Land Bridge National Monument was established 1 December 1978, by President Jimmy Carter using his authority under

3268-626: The Trail Creek Caves, Kuzitrin Lake and Agulaak Island. The Denbigh culture was followed by the Choris culture, which brought pottery and ground stone tools. Cape Espenberg, the Trail Creek Caves and the region around Lopp Lagoon were occupied during this time. This was followed by the Ipuitak culture from about 1900 BC to 1000 BC, at many of the same locations. The Northern Maritime tradition followed, comprising

3344-655: The U.S. Forest Service, and the Bureau of Land Management manage areas called national monuments . National Wilderness Areas are designated within other protected areas, managed by various agencies and sometimes wilderness areas span areas managed by multiple agencies. Those relying on U.S. protected areas data are advised to learn more about all of these conventions by reviewing the extensive PAD-US Help system . There are existing federal designations of historic or landmark status that may support preservation via tax incentives, but that do not necessarily convey any protection, including

3420-464: The authority of the Antiquities Act . The designation was modified in 1980 to a national preserve with the passage of the Alaska National Interest Lands Conservation Act (ANILCA), which would allow both subsistence hunting by local residents and sport hunting. The preserve includes significant archaeological sites and a variety of geological features. The preserve has seen recent volcanic activity, with lava flows and lake-filled maars . Hot springs are

3496-476: The basalt/andesite field of the QAPF diagram. Basalt is further distinguished from andesite by its silica content of under 52%. It is often not practical to determine the mineral composition of volcanic rocks, due to their very small grain size, in which case geologists instead classify the rocks chemically, with particular emphasis on the total content of alkali metal oxides and silica ( TAS ); in that context, basalt

3572-475: The characteristic igneous rocks formed at mid-ocean ridges. They are tholeiitic basalts particularly low in total alkalis and in incompatible trace elements, and they have relatively flat REE patterns normalized to mantle or chondrite values. In contrast, alkali basalts have normalized patterns highly enriched in the light REE, and with greater abundances of the REE and of other incompatible elements. Because MORB basalt

3648-700: The coast to include Ikpek Lagoon . A narrow corridor connects the Ikpek Lagoon section to the main preserve. The interior portions extend to and across the Continental Divide as far as the Bendeleben Mountains . The region around the continental divide includes volcanic areas such as Serpentine Hot Springs and lava fields between the Noxapaga River and the Kuzitrin River . The preserve's high point

3724-513: The coastal plain, where they form a system of lagoons and barrier bars or spits. The rolling uplands lie inland and to the south of the coastal plain. The Serpentine Hot Springs and Trail Creek Caves are in this region of limestone, marble and other minerals. Volcanic activity in the interior has left areas of basalt on the Imuruk lava plateau. The volcanic activity has been recent: the Lost Jim lava flow

3800-447: The crust, forming an apron of mixed basalt and wall rock breccia and a fan of basalt tuff further out from the volcano. Amygdaloidal structure is common in relict vesicles and beautifully crystallized species of zeolites , quartz or calcite are frequently found. During the cooling of a thick lava flow, contractional joints or fractures form. If a flow cools relatively rapidly, significant contraction forces build up. While

3876-569: The earliest undisputed evidence of human occupation are relics of the Paleo-Arctic tradition found in the Trail Creek Caves and dating to between 10,000 and 7,000 BC. Archaeological evidence suggests a gap in human occupation on the peninsula until about 4200 BC. Materials from the period 4000 to about 2000 BC, known as the Denbigh culture of the Arctic small tool tradition , have been found at Cape Espenberg,

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3952-541: The evolution of the Earth's mantle . Isotopic ratios of noble gases , such as He / He, are also of great value: for instance, ratios for basalts range from 6 to 10 for mid-ocean ridge tholeiitic basalt (normalized to atmospheric values), but to 15–24 and more for ocean-island basalts thought to be derived from mantle plumes . Source rocks for the partial melts that produce basaltic magma probably include both peridotite and pyroxenite . The shape, structure and texture of

4028-585: The four largest and northernmost maar lakes in the world at Espenberg , formed by phreatomagmatic eruptions leaving round craters. The ages of the lakes range from 100,000–200,000 years at Whitefish Maar, to 50,000 years at North Killeak Maar, 40,000 years at South Killeak Maar, and 17,500 years at Devil Mountain Maar. The action of ice and permafrost produces features such as polygonal ice wedges and pingos . Serpentine Hot Springs, ( Inupiaq :  Iyat or Uunaatuq ), previously known as Arctic Hot Springs,

4104-493: The glacial epoch this bridge was a migration route for people, animals, and plants whenever ocean levels fell enough to expose the land bridge. Archeologists disagree whether it was across this Bering Land Bridge , also called Beringia , that humans first migrated from Asia to populate the Americas, or whether it was via a coastal route . Bering Land Bridge National Monument was established in 1978 by Presidential proclamation under

4180-410: The hot springs site was very strong. Most of the land in the preserve is tundra , underlain by permafrost. The tundra supports a variety of low and slow-growing plants. The landscape is dominated by grasses and sedges, such as cottongrass . Large trees cannot survive on the tundra. Tree species are limited to dwarf species like Arctic willow , Alaska willow and dwarf birch . Berry-bearing plants in

4256-708: The islands of Hawaiʻi , the Faroe Islands , and Réunion . The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is the rock most typical of large igneous provinces . These include continental flood basalts , the most voluminous basalts found on land. Examples of continental flood basalts included the Deccan Traps in India , the Chilcotin Group in British Columbia , Canada ,

4332-604: The magma as it decompresses during its approach to the surface; the erupted lava then solidifies before the gases can escape. When vesicles make up a substantial fraction of the volume of the rock, the rock is described as scoria . The term basalt is at times applied to shallow intrusive rocks with a composition typical of basalt, but rocks of this composition with a phaneritic (coarser) groundmass are more properly referred to either as diabase (also called dolerite) or—when they are more coarse-grained (having crystals over 2 mm across)—as gabbro . Diabase and gabbro are thus

4408-416: The magma to the surface, embedded in a finer-grained matrix . These phenocrysts are usually made of augite, olivine , or a calcium-rich plagioclase, which have the highest melting temperatures of any of the minerals that can typically crystallize from the melt, and which are therefore the first to form solid crystals. Basalt often contains vesicles ; they are formed when dissolved gases bubble out of

4484-704: The mantle. Many alkali basalts may be formed at greater depths, perhaps as deep as 150–200 km. The origin of high-alumina basalt continues to be controversial, with disagreement over whether it is a primary melt or derived from other basalt types by fractionation. Relative to most common igneous rocks, basalt compositions are rich in MgO and CaO and low in SiO 2 and the alkali oxides, i.e., Na 2 O + K 2 O , consistent with their TAS classification . Basalt contains more silica than picrobasalt and most basanites and tephrites but less than basaltic andesite . Basalt has

4560-406: The most voluminous of all volcanic formations. Basaltic magmas within Earth are thought to originate from the upper mantle . The chemistry of basalts thus provides clues to processes deep in Earth's interior . Basalt is composed mostly of oxides of silicon, iron, magnesium, potassium, aluminum, titanium, and calcium. Geologists classify igneous rock by its mineral content whenever possible;

4636-1054: The native caribou, Siberian tundra reindeer ( Rangifer tarandus sibiricus ) were introduced in 1894, reaching a peak population of 600,000 animals in the 1930s. The herd has since been reduced to about 4,000. The Reindeer Act of 1937 prohibited ownership by non-Native Americans, and the reduced herds were managed by natives from that time onward. Other mammals in the preserve are walruses , polar bears , red foxes , brown bears , Arctic foxes , ribbon seals , wolverines and beavers . Significant nesting bird species include sandhill cranes and yellow-billed loons . The Seward Peninsula's rivers and streams are habitat for freshwater fish and for anadromous salmon species. The principal salmon species are chinook , coho , sockeye , chum and pink salmon. Other salmonids such as Dolly Varden trout and Arctic grayling remain in freshwater throughout their life cycle. The preserve also harbors northern pike and other fish. The preserve has weather typical of northwestern Alaska, with long cold winters. Weather

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4712-410: The oldest samples are 4.2 billion years old, and the youngest flows, based on the age dating method of crater counting , are estimated to have erupted only 1.2 billion years ago. From 1972 to 1985, five Venera and two VEGA landers successfully reached the surface of Venus and carried out geochemical measurements using X-ray fluorescence and gamma-ray analysis. These returned results consistent with

4788-670: The park, some 3,000,000 acres (1,200,000 ha), is state-owned and preserved as "forever wild" by the Forest Preserve of New York . Wood-Tikchik State Park in Alaska is the largest state park by the amount of contiguous protected land; it is larger than many U.S. National Parks, with some 1,600,000 acres (650,000 ha), making it larger than the state of Delaware . Many states also operate game and recreation areas. U.S. counties, cities and towns, metropolitan authorities, regional park systems , recreation districts and other units manage

4864-432: The preserve features a variety of wildflowers, including Alpine Arnica , fireweed , Kamchatka rhododendron , Labrador tea , monkshood , one-flowered cinquefoil , harebell and alpine forget-me-not . Caribou are survivors of the ice age environment in the preserve, together with reintroduced muskoxen . The muskoxen were reintroduced to the area in 1970, after being wiped out in the early 20th century. In addition to

4940-420: The preserve include bog blueberry , crowberry , low-bush cranberry and cloudberry or salmonberry . Lichens are found in rocky areas, including Cetraria , Cladina , Cladonia , Xanthoria and Umbilicaria genera. Mosses and liverworts in the preserve include Sphagnum peat mosses, Aulacomnium bog mosses, Dicranum forked mosses, Polytrichum haircap mosses and Rhizomnium . In spring

5016-622: The preserve include the Trail Creek Caves , Devil Mountain Lakes , and the Lost Jim Lava Flow . The Seward Peninsula is a remnant of the Beringia subcontinent that linked Alaska and Siberia during periods of low sea levels during ice ages . The region was mostly untouched by glaciers during the ice age. The preserve lands can be described by five physiographic zones: the northern coastal plan,

5092-475: The rate of cooling; very rapid cooling may result in very small (<1 cm diameter) columns, while slow cooling is more likely to produce large columns. The character of submarine basalt eruptions is largely determined by depth of water, since increased pressure restricts the release of volatile gases and results in effusive eruptions. It has been estimated that at depths greater than 500 metres (1,600 ft), explosive activity associated with basaltic magma

5168-411: The relative volume percentages of quartz (crystalline silica (SiO 2 )), alkali feldspar , plagioclase , and feldspathoid ( QAPF ) are particularly important. An aphanitic (fine-grained) igneous rock is classified as basalt when its QAPF fraction is composed of less than 10% feldspathoid and less than 20% quartz, and plagioclase makes up at least 65% of its feldspar content. This places basalt in

5244-586: The remaining population of muskoxen are currently in Gates of the Arctic National Park and Preserve as well as a local farm in Palmer which has been existing since the mid-1950s. The Seward Peninsula, as part of Beringia, was a path for the migration of Asian peoples into the Americas. The earliest artifacts found in the area are modified animal bones dating to about 13,000 BC. These are not considered definitive, and

5320-595: The robotic Russian Luna program , and are represented among the lunar meteorites . Lunar basalts differ from their Earth counterparts principally in their high iron contents, which typically range from about 17 to 22 wt% FeO. They also possess a wide range of titanium concentrations (present in the mineral ilmenite ), ranging from less than 1 wt% TiO 2 , to about 13 wt.%. Traditionally, lunar basalts have been classified according to their titanium content, with classes being named high-Ti, low-Ti, and very-low-Ti. Nevertheless, global geochemical maps of titanium obtained from

5396-403: The rock at the landing sites being basalts, including both tholeiitic and highly alkaline basalts. The landers are thought to have landed on plains whose radar signature is that of basaltic lava flows. These constitute about 80% of the surface of Venus. Some locations show high reflectivity consistent with unweathered basalt, indicating basaltic volcanism within the last 2.5 million years. Basalt

5472-546: The rolling stream-dissected uplands, the Imuruk lava plateau, the Kuzitrin flats, and the Bendeleben Mountains. The Seward Peninsula is primarily composed of metamorphic blueschist , with deposits of sand, gravel, silt, loess and a few glacier-deposited moraines . The area around Cape Espenberg includes a series of relict beach ridges like those found farther north at Cape Krusenstern . These deposits are found mainly in

5548-455: The sea it usually forms pillow basalts. However, when ʻaʻā enters the ocean it forms a littoral cone , a small cone-shaped accumulation of tuffaceous debris formed when the blocky ʻaʻā lava enters the water and explodes from built-up steam. The island of Surtsey in the Atlantic Ocean is a basalt volcano which breached the ocean surface in 1963. The initial phase of Surtsey's eruption

5624-648: The term "basalt" to the volcanic black rock beneath the Bishop of Meissen's Stolpen castle , believing it to be the same as the "basaniten" described by Pliny the Elder in AD ;77 in Naturalis Historiae . On Earth, most basalt is formed by decompression melting of the mantle . The high pressure in the upper mantle (due to the weight of the overlying rock ) raises the melting point of mantle rock, so that almost all of

5700-580: The upper mantle is solid. However, mantle rock is ductile (the solid rock slowly deforms under high stress). When tectonic forces cause hot mantle rock to creep upwards, pressure on the ascending rock decreases, and this can lower its melting point enough for the rock to partially melt , producing basaltic magma. Decompression melting can occur in a variety of tectonic settings, including in continental rift zones, at mid-ocean ridges , above geological hotspots , and in back-arc basins . Basalt also forms in subduction zones , where mantle rock rises into

5776-400: Was highly explosive, as the magma was quite fluid, causing the rock to be blown apart by the boiling steam to form a tuff and cinder cone. This has subsequently moved to a typical pāhoehoe-type behaviour. Volcanic glass may be present, particularly as rinds on rapidly chilled surfaces of lava flows, and is commonly (but not exclusively) associated with underwater eruptions. Pillow basalt

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