CE 211 - Igneous Rocks and Rock Cycle Quiz

Igneous Rock Textures & Terms

• Aphanitic describes very fine-grained igneous rocks.
• Porphyritic texture is characterized by the presence of both coarse and fine-grained minerals.
• Glassy texture is formed when magma or lava cools very quickly, resulting in a glassy appearance.
• Pyroclastic refers to the ejection of fragmented rock material from a volcanic eruption.
• Phaneritic texture is characterized by very large, coarse-grained minerals.
• A'a lava flows have a rough, jagged surface called clinkers.
• Igneous rocks with glassy textures are called obsidian.
• Pyroclastic rocks are formed by explosive volcanic eruptions.
• Pegmatite is an igneous rock with a coarse-grained, pegmatitic texture.
• A'a lava flows have a rough, clinkery surface.
• Rhyolite is an extrusive igneous rock.
• Intrusive igneous rocks cool slowly beneath the Earth's surface while extrusive igneous rocks cool quickly above the surface.
• Felsic igneous rocks contain more light-colored feldspars and silica than dark-colored minerals.
• Mafic igneous rocks are known for containing mostly darker silicate minerals and calcium-rich plagioclase feldspar, with little quartz.
• Quartz is the primary mineral in granitic rocks that makes up about 70% of the Earth's crust.
• Mafic igneous rocks tend to be more dense than granitic rocks.
• Intermediate igneous rocks have a composition between granites and basalts, with approximately 25% dark silicate minerals.
• A'a lava with a rough, jagged surface texture is called blocky lava.

Test your knowledge on the origin of magma in relation to plate tectonics, Bowen’s Reaction Series, mineral crystallization, melting temperatures, rock compositions, textures, and classification of igneous rocks.