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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 ...
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]
Debris flows with volumes ranging up to about 100,000 cubic meters occur frequently in mountainous regions worldwide. The largest prehistoric flows have had volumes exceeding 1 billion cubic meters (i.e., 1 cubic kilometer). As a result of their high sediment concentrations and mobility, debris flows can be very destructive.
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.
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]
Furthermore, the ability to flow may also be dependent upon the amount of energy transferred to the falling sediment throughout the failure event. Often large landslides on the continental margin are complicated and components of slide, debris flow and turbidity current may all be apparent when examining the remains of a submarine landslide.
The Mount Meager massif is a group of volcanic peaks in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada.Part of the Cascade Volcanic Arc of western North America, it is located 150 km (93 mi) north of Vancouver at the northern end of the Pemberton Valley and reaches a maximum elevation of 2,680 m (8,790 ft).
Mt. Cayley massif, south aspect. The volcano resides in the middle of a north–south trending zone of volcanism called the Mount Cayley volcanic field. [3] It consists predominantly of volcanoes that formed subglacially during the Late Pleistocene age, such as Pali Dome, Slag Hill, Ring Mountain and Ember Ridge, but activity continued at Pali Dome and Slag Hill into the Holocene epoch.