quiz / lecture 4

What are the 3 types of rocks?

igneous, sedimentary, metamorphic

igneus rock

Rock formed by the cooling of lava or magma.

Extrusive

Igneous rock that forms from lava on Earth's surface

intrusive

Magma cools very slowly - allows minerals to forms. Therefore get large crystals

What does the rate of cooling do?

Rapid cooling results in the formation of a solid mass of small intergrown crystals.

Classification by composition 1

Felsic High Silica content: equal to or greater than 63%

Classification by composition 2

Mafic low silica content: Between 43% and 53% silica.

Phaneritic

coarse grained, cooled slowly

Aphanitic

fine grained, cooled quickly

Glassy

looks like broken glass, cooled very quickly

2 types of volcanic eruptions

quiet and explosive

Quiet-type Eruption

eruption occurs with little magma that flows onto the surface of earth.

Explosive-type Eruption

eruption occurs with one or a few violent explosions that last a few hours

What leads to volcanic explosions

high viscosity magma and high gas pressure