Crater Lake

Crater Lake is the remnant of a volcano formerly known as Mount Mazama. It is located 97 km NW of Klamath Falls, OR.

As we know it today, Crater Lake is the deepest lake in the United States and sits at an elevation of more than 6000 feet. Underneath the water lies an ancient yet still active volcano - Mount Mazama. Around 7,700 years ago, a major series of eruptions occurred, working in tandem with further volcanic ejections via fractures to cause the peak to collapse and form a caldera several miles in diameter. This was the largest known eruption from a Cascade Range volcano.

Subsequent, smaller eruptions continued within the newly formed caldera, forming present-day Wizard Island - a conical-shaped mound at the east end of the lake - and two others on the caldera floor. Over hundreds of years following the initial eruption, continuous snow and rainfall accumulated in Mazama’s caldera and formed the lake itself. Modern water levels are now kept at an average of 1,943 feet in depth through the balance of regular precipitation, continuous evaporation, and seepage through the porous layers of volcanic rock.

In the most recent known eruption, a small lava dome grew on the flank of the Wizard Island edifice about 4,800 years ago. Crater Lake is still hydrothermally active.

More background information on Crater Lake

Background Seismicity

The Cascades Volcano Observatory and the PNSN cooperatively operate 4 seismometers on or near Crater Lake. On average, we locate 0 to 1 earthquakes within 10 km of the volcano each decade.