• 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?