Week 7 Study Questions – Magma, Lava, and Igneous Rocks

These flashcards cover key concepts and definitions related to magma, lava, and different types of igneous rocks, enhancing understanding for exam preparation.

Lava

Magma that has reached Earth’s surface through a volcanic eruption or fissure.

Magma

Molten rock that remains underground, stored in magma chambers or moving through cracks in the crust.

Decompression Melting

Occurs when mantle rock rises towards the surface, pressure drops faster than temperature, allowing rock to melt.

Volatiles

Substances like water or CO2 that lower the melting point of rock.

Viscosity

The resistance of a substance to flow; high viscosity means thicker and more resistant to flow.

Mafic Magma

Magma that is low in silica (45–52%) and high in iron and magnesium, producing dark colored rocks like basalt and gabbro.

Intermediate Magma

Magma with silica content between 52–65% and moderate iron and magnesium levels, producing rocks like andesite and diorite.

Felsic Magma

Magma that has more than 65% silica, low in iron and magnesium, resulting in light-colored rocks like rhyolite and granite.

Fractional Crystallization

The process where minerals solidify from magma in a predictable order, altering the composition of the remaining melt.

Pegmatitic Texture

A texture where large mineral crystals are formed, indicative of slow cooling in a magma chamber.