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John Day Fossil Beds National Monument is a U.S. national monument in Wheeler and Grant counties in east-central Oregon.Located within the John Day River basin and managed by the National Park Service, the park is known for its well-preserved layers of fossil plants and mammals that lived in the region between the late Eocene, about 45 million years ago, and the late Miocene, about 5 million ...
Before a storm that can potentially nucleate debris flows, forecasting frameworks can often quantify the likelihood that a debris flow might occur in a watershed; [18] however, it remains challenging to predict the amount of sediment mobilized and therefore, the total size of debris flows that may nucleate for a given storm, and whether or not ...
Prehistoric sector collapses are stored in the geological record [1] in the form of debris avalanche deposits [2] and collapse scars. Debris avalanche deposits can be found up to 20 km from the site of collapse. [3] Studying avalanche deposits informs on the time scale of the collapse and the volcano from which it originated. [2]
Most of the lava continued to flow westward through Klastline Valley and reached the Stikine River. [121] [131] Lava flows overlying sediment at the mouth of the Tahltan River. Lava of the Klastline eruptive period continued to flow 55 kilometres (34 miles) downstream along the Stikine River from its confluence with the Klastline River. [142]
The eruption of overlapping andesitic lava flows accumulated to build the volcano. By the time it reached its peak size, the volcano was immense, measuring at its base between 11 mi (18 km) and 15 mi (24 km) wide and more than 11,000 ft (3,353 m) tall. [7] Activity at Brokeoff lasted for approximately 200,000 years.
The map of North America with the Western Interior Seaway during the Campanian. The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses for 34 million years.
Large masses of material are moved in debris flows, hyperconcentrated mixtures of mud, clasts that range up to boulder-size, and water. Debris flows move as granular flows down steep mountain valleys and washes. Because they transport sediment as a granular mixture, their transport mechanisms and capacities scale differently from those of ...
Most flows are liquefied, and many references to fluidized sediment gravity flows are in fact incorrect and actually refer to liquefied flows. [5] Debris flow or mudflow – Grains are supported by the strength and buoyancy of the matrix. Mudflows and debris flows have cohesive strength, which makes their behavior difficult to predict using the ...