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In Bering Land Bridge National Preserve · pagina 11 di 11
Bering Land Bridge National Preserve, on Alaska's Seward Peninsula, protects the eastern end of a lost continent. During the ice ages of the Pleistocene, when sea level fell, a strip of land about 620 miles (1,000 km) wide joined Alaska to Siberia where the Bering and Chukchi seas now lie in shallow water. Plants, animals and — probably among the first to reach North America — people crossed it. The preserve's archaeology, fossils and living things record that history, and its geology is much of the reason it exists.
The preserve in brief
| Established | as a national monument, December 1, 1978; redesignated a national preserve, December 2, 1980 |
| Where | Seward Peninsula, northwestern Alaska (Northwest Arctic Borough and Nome Census Area) |
| Size | about 2.7 million acres |
| The land bridge | exposed during the glaciations of the Pleistocene, 2.58 million to 11,700 years ago |
| Geologic highlights | lava flows and explosive ash deposits, coastal landforms, fossil sites, Serpentine Hot Springs |
Four kinds of bedrock
| Group | What it is | Where |
|---|---|---|
| Nome Complex | a late Proterozoic carbonate platform, since metamorphosed | widespread |
| York terrane | lightly metamorphosed layered rocks | near Ear Mountain, in the west |
| High-grade metamorphic complexes | strongly metamorphosed rock wrapped around Cretaceous granite bodies | the Kigluaik, Bendeleben and Darby mountains |
| Mesozoic and Cenozoic igneous rocks | Cretaceous plutons and intrusions, and the young volcanic rocks of the Imuruk and Espenberg volcanic fields | scattered; the volcanic fields in the preserve's interior and north |
The volcanic fields are where the preserve is most striking — lava plains, and explosion craters from eruptions that met permafrost and groundwater.
Maps and reports
The Park Service's Geologic Resources Inventory has published a scoping summary, digital geologic maps and a geologic report for the preserve (Lanik and others, 2019), free on the NPS DataStore.
Sources
Written from "NPS Geodiversity Atlas—Bering Land Bridge National Preserve, Alaska", National Park Service Geologic Resources Division, a work of the United States government in the public domain, which cites Lanik et al. (2019), Till et al. (2011) and Hopkins (1963, 1967).
In queste raccolteBering Land Bridge National Preserve
Licenza: CC0 1.0 (pubblico dominio) · Tratto da www.nps.gov
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