Geologic Setting
Lava Beds lies on the northern flank of Medicine Lake volcano which, like Mount Shasta, is part of this mountain range.
What is the High Cascade Range?
Basalt lava that is very fluid develops a thin skin on its surface that is folded to produce this texture.
What is ropy or pahoehoe texture?
Formed by small, soft globs of lava piled up close to their vents, Fleener's Chimneys are this type of volcano.
What is a spatter cone?
Lavas that are less than 60,000 years old and have charred trees or other organic matter can be dated using this technique.
What is radiocarbon dating?
Steep normal faults, like those that produced a M 6 earthquake in nearby Klamath Falls in 1992, are exposed in the monument at __________.
What is Gillem Bluff?
Steep faults and low valley floors indicate Lava Beds is in the Basin and Range Province, a region undergoing this process.
What is stretching or extension?
"Dry" basalt lavas form beneath Medicine Lake volcano as this soft layer of the mantle flows up towards the surface and melts due to decompression.
What is the asthenosphere?
Skull Cave is not a cave or cavern in the traditional sense but, rather, is this type of feature.
What is a lava tube?
Earth's magnetic field, whose reversals help us date some lavas at Lava Beds, originates in this part of the planet.
What is the core?
About 180,000 years ago dense clouds of hot rock fragments and gas called __________ swept down the northern flank of the Medicine Lake Volcano and deposited the Tuff of Anderson Well across the monument.
What are pyroclastic flows?
Mount Shasta and the Medicine Lake volcano lie above the Cascadia subduction zone which is this type of plate boundary?
What is a convergent boundary?
Small pieces of white, bubbly glass that erupted from Glass Mountain about 900 years ago and now blanket Lava Beds are this type of rock.
What is pumice?
Formed by a relatively gas rich lava, conical hills with funnel-shaped craters that are made up of small pieces of lava that cooled while flying through the air are this type of volcano.
What is a cinder cone?
About 62,000 years ago lava built this prominent cinder cone near the center of the monument that we climbed for a great view.
What is Schonchin Butte?
Today, violent steam explosions like those that built the Petroglyph Point tuff cone 270,000 years ago are unlikely because this body of water was diked and drained to create farmland.
What is Tule Lake?
The Basin and Range Province began to stretch apart as the western part of North America was dragged northwestward by the Pacific plate along this well known geologic structure.
What is the San Andreas fault?
Basalt lava that is relatively cool and stiff develops a rough surface covered with small broken pieces (clinkers) giving it this distinctive texture.
What is blocky or aa texture?
Formed by steam explosions as lava came up into Tule Lake, Petroglyph Point is this type of volcano.
What is a tuff cone?
About 36,000 years ago basalt lava that covers roughly 70% of Lava Beds erupted from this vent.
What is Mammoth Crater?
Rapid melting of winter snow by an eruption on the Medicine Lake Volcano could send these dense slurries of rock and water northward into the monument.
What are debris flows?
Earth's tectonic plates are made of the crust plus the uppermost rigid mantle, a combination known as the _____.
What is the lithosphere?
Lavas that rise into the crust beneath Mount Shasta are formed by the melting of the mantle due to the release of this compound from the sinking Gorda plate.
What is water?
Mammoth Crater, a depression created by collapse of the surface when lava in an underlying reservoir drained away, is this type of volcanic vent.
What is a pit crater?
This young lava erupted from a vent on the western side of the monument and built Fleener's Chimneys.
What is the Devil's Homestead Andesite?
The growth of this type of volcano, perhaps accompanied by the fall of tephra downwind and a lava flow, is the most likely volcanic hazard to threaten Lava Beds National Monument.
What is a cinder cone?