China Hat Geological Site

China Hat Geological Site (HM2020)

Location: Soda Springs, ID 83276 Caribou County
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Country: United States of America
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N 42° 49.163', W 111° 33.588'

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Noticeable for their distinct shapes, China Hat and nearby China Cap are rhyolite domes that intruded and pierced the basalt of the Blackfoot Lava Field. The basaltic phase of this volcanic province was active in middle Pleistocene around 500,000 years ago, whereas the rhyolitic dome-building phase is younger. The combination of these two compositional types in a single area is known as bimodal volcanism.
The dome of molten rock was formed from melted rock within the crust of the Earth. As rock melted, it became less dense than the surrounding rock and rose toward the surface of the Earth. Molten rock reached the surface, forming domes at China Hat, China Cap, and North Cone. Locally on the sides and tops of these cones were eruptions and flows of pumice, a gas-rich spongy rhyolite.
When the forces driving the basalt to the surface subsided, molten lava chambers high in the crust drained back toward the region where it originated. As these chambers emptied, they collapsed producing depressions at the land surface as a can be seen by the broken surface of the Blackfoot Lava Field around China Hat.
This area and other parts of the lava field contain sub-parallel northward trending faults in the basalt lave flows. These reflect extension in an east-west direction, perhaps related to intrusion of the domes. The faults create
an intriguing landscape west of here, consisting of "grabens" (German of grave). which are elongated depressions created when blocks of crust dropped down in response to extension. Steep cliffs in the lava and linear piles of lava blocks mark the fault locations.
HM NumberHM2020
Marker ConditionNo reports yet
Date Added Sunday, July 23rd, 2017 at 1:02pm PDT -07:00
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Locationbig map
UTM (WGS84 Datum)12T E 454238 N 4740909
Decimal Degrees42.81938333, -111.55980000
Degrees and Decimal MinutesN 42° 49.163', W 111° 33.588'
Degrees, Minutes and Seconds42° 49' 9.7799999999998" N, 111° 33' 35.28" W
Driving DirectionsGoogle Maps
Area Code(s)208
Which side of the road?Marker is on the right when traveling West
Closest Postal AddressAt or near 2780 ID-34, Soda Springs ID 83276, US
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