Igneous Landforms and Volcanic Activity

Flashcards covering key terms and concepts from the lecture on igneous landforms and volcanic activity.

Volcanic landform

A surface feature created by volcanic activity.

Viscosity

Resistance to flow.

Factors that increase viscosity

↑ Silica, ↑ crystals, ↑ gases, ↓ temperature.

Mafic

Refers to magma or igneous rocks that are low in silica and result in low viscosity.

Felsic

Refers to magma or igneous rocks that are high in silica and result in high viscosity.

Vesicles

Holes formed in volcanic rock due to trapped gases.

Basalt plateaus

Large Igneous Provinces characterized by thick layers of flood basalts.

Shield volcanoes

Volcanoes with broad, gentle slopes due to low lava viscosity, mainly mafic (basalt).

Aa lava

Rough, slow-moving lava.

Pahoehoe lava

Smooth, fast-moving lava.

Pillow basalts

Basalt formations created from underwater eruptions.

Cinder cones

Volcanic cones made entirely of pyroclasts.

Pyroclasts

Fragments of volcanic material ejected during eruptions.

Agglomerate

A rock consisting of large angular volcanic fragments.

Sunset Crater

A cinder cone known for its red color due to oxidized iron.

Composite volcanoes

Volcanoes with high viscosity, explosive eruptions, consisting of layers of lava flows and ash.

Porphyritic texture

A rock texture characterized by large crystals in a fine-grained matrix.

Pyroclastic flow

A fast-moving avalanche of hot gas and ash.

Lahar

A mudflow that consists of a mixture of volcanic ash and water.

Lava domes

Mounds formed from thick lava and ash, typically high-silica.

Talus

The broken rock fragments that accumulate at the base of a slope.

Collapse caldera

A depression formed when a volcano's roof collapses after a massive eruption.

Crater Lake

A collapse caldera that has filled with water.

Plutonic rocks

Rocks that form deep underground.

Dike vs. Sill

Dike: vertical intrusion; Sill: horizontal intrusion.

Granite minerals

Composed primarily of quartz, feldspar, and mica.

Gabbro minerals

Mainly composed of plagioclase feldspar and pyroxene.

Batholith

A large-scale igneous intrusion greater than 100 km².

Stone Mountain

A granite rock type, known for its prominence.

Elberton Batholith

A granite formation used for monuments and building stone.

Sierra Nevada Batholith

A large granite body forming the Sierra Nevada mountain range.