• Wizard Island

    Crater Lake

    National Park Oregon

The geology of Crater Lake National Park

Geologic features of Crater Lake National Park:

Mount Mazama
  • the eruption of Mount Mazama, about 7,700 years ago, lasted only a couple of days
  • the first phase of the eruption produced a towering column of pumice and ash
  • the second phase of the eruption was the ring-vent phase that started the collapse of the mountain into the center
    • pyroclastic flows happened in this phase (mixture rock fragments, gas, ash at temperatures > 1470 degrees F)
Mazama Ash
  • ash rose and settled over much of the western US and southwestern Canada (656,000 miles squared)
  • the ash makes a good marker for geologists to study features and processes over a wide variety of landscapes
Shield Volcanoes and Cinder Cones
  • partly surround Mount Mazama
  • part of the historic magma input to Mount Mazama
  • activity of these small volcanoes represents activities of regional volcanism
Crater Lake Caldera and rocky fill
  • the caldera is 5-6 miles in diameter
  • the caldera is 3,900 feet deep
  • since the eruption, material has fallen into the caldera from the walls, and from new volcanic activity inside the caldera
Crater Lake
  • average surface elevation 6,178 feet above sea level
  • maximum depth 1,949 feet
  • deepest lake in US
  • second deepest in North America
  • seventh deepest in with world
  • the lake is one of the most clear in the world
  • the blue color of the lake is one of the treasures of the world
  • scientific study began as early as 1887
  • the lake has no stream running in or out
  • the lake water level is controlled by precipitation, evaporation, and seepage through the rocks
Glacial Features
  • in the past, glaciers and volcanoes occurred at Crater Lake during the known global ice ages
  • glacial features include
    • ice-bounded lava flow formations
    • table mountains
    • till and moraines
    • polish and striations
    • U-shaped valleys
    • notches, cirques, and horns
    • six advances of glacial ice occurred at Crater Lake National Park
    • carved notches at the beginnings of Sun and Kerr valleys
    • one advance happened on the caldera walls
Caves
  • the park contains more than 40 caves
  • 31 caves are within the rim of the caldera
  • many caves are near the lake surface
  • 5 cave sites (with one or more caves) occur outside the rim

Did You Know?

Did You Know?

Seven different trees live on Phantom Ship, an island in Crater Lake. There are also colonies of violet green swallows, and several varieties of wildflowers and lichens living there.