Exam 4: Igneous Rocks and Plutons

Mafic lava tends to be fluid, whereas felsic lava is much more viscous.

The intrusive igneous rocks that most likely formed below Earth's surface are ____.

A laccolith forms when a sill ____ and causes the overlying rocks to ____.

Most lava temperatures are taken at volcanoes that show little or no explosive activity because ____.

You are given a specimen of rhyolite and a specimen of granite. What method would you use to differentiate them? How can you tell which specimen is more likely volcanic and which is more likely plutonic? Include the terms phaneritic and aphanitic in your answer.

Why do holes form in vesicular igneous rocks?

Discuss three (3)mechanisms of magma origination.

Basalt cooled from ____________________, whereas granite cooled from ____________________.

Igneous rocks with a texture that is so fine-grained that the crystals are too small to see are ____.

Volcanoes have a cylindrical conduit know as a volcanic ____ that connects to an underlying magma chamber.

Magmas with the highest percentages (> 65%)of silica are called ____.

Bowen's reaction series explains the order of mineral formation with decreasing pressure.

Igneous rocks formed by explosive volcanic activity have a texture that is ____.

Large crystals found in a fine-grained groundmass can indicate a(n)____.

The largest plutons are called ____________________ and are made up primarily of ____________________ igneous rocks.

Obsidian, a variety of volcanic glass, may be black, dark gray, red, or brown, depending on the presence of iron.

Mantle plumes are primarily found at ____.

Laccoliths are dikes that inflate, causing the overlying rock to bow upward.