How does a crater form in a volcano

And other craters are volcanic in origin. A volcano crater is a circular depression around a volcanic vent. This is where the lava, ash and rock erupt out of a volcano. In most situations, the volcano crater is located at the top of the volcano.

Think of a classic cone-shaped volcano, with steep sides and a slightly flattened top. If you could climb up to the top of the volcano and peer over the edge, you would look down into the volcano crater. Leaving no support for this massive dome, the roof of the magma chamber collapsed, forming the bowl-shape depression known as a caldera. About 5, to 6, years ago, the accumulation of rain and snow filled the caldera.

It took perhaps years for the caldera to fill to its present-day lake level, which is maintained by a balance between precipitation and evaporation plus seepage.

Note: The description on this page is a general overview about the formation of Crater Lake. For more in depth studies and technical descriptions, please see the following sites:. The major volcanoes of the Cascades include the following listed from south to north : California: Lassen Peak and Mount Shasta. GREW Mount Mazama was a large composite volcano that was built during the past , years by hundreds of smaller eruptions of lava flows.

BLEW About 7, years ago, Mount Mazama erupted catastrophically, blowing out about 50 km 3 12 mi 3 of magma as pyroclastic materials mostly rhyodacite pumice and fine ash in at most a few days.

Where had all this mass gone? Did Mount Mazama blow its top off? But no matter at what angle it makes contact, the enormous amount of kinetic energy the projectile carries immediately transfers to the target rock it hits, triggering powerful shock waves. Although craters look like imprints of a giant fist smashing the ground inward, impact shock waves have the opposite effect, which planetary scientists divide into three phases. The compression stage of crater formation involves that initial exchange of energy between the projectile and the impact area.

During the excavation phase, the massive shock wave causes the projectile to simultaneously melt and vaporize, spewing plumes of searing hot rock vapor miles high into the atmosphere. The force can catapult chunks of molten and solid rock hundreds of miles from the impact site — this material is known as ejecta flow. During the final modification phase, the remainder of ejecta partially refills and rings the crater site, and debris forms a rich mineral composite called breccia.

Larger, more forceful impact events will form complex craters in which the rock at the center of the crater rebounds from the downward pressure of the shock wave and uplifts into a mound-like formation.