Volcanos

Question 1

Andesitic Lava

Answer 1

-lower temps than basalts
-higher silica content
-slower flow, lump in sticky masses
“A lava of intermediate composition that has a higher silica content than basalt, erupts at lower temperatures, and is more viscous. Extrusive equivalent of diorite.”

Question 2

Ash-flow deposit

Answer 2

An extensive sheet of hard volcanic tuff.

Question 3

Basaltic lava

Answer 3

A lava of mafic composition that has a low sil- ica content, erupts at high temperatures, and flows readily. Ex- trusive equivalent of gabbro.

Question 4

Caldera

Answer 4

A large, steep-walled, basin-shaped depression formed after a violent eruption in which large volumes of magma are discharged, when the overlying volcanic structure collapses catastrophically through the roof of the emptied magma chamber.

Question 5

Crater

Answer 5

A bowl-shaped pit found at the summit of most volcanoes, centered on the vent.

Question 6

Fissure Eruption

Answer 6

A volcanic eruption emanating from an elon- gate fissure rather than a central vent.

Question 6

Flood basalt

Answer 6

An immense basaltic lava plateau extending many kilometers in flat, layered flows originating from fissure eruptions.

Question 7

Hot spot

Answer 7

A volcanic center found at the beginning of pro- gressively older aseismic ridges or within a continent far from a plate boundary. Hypothesized to be the surface expression of a mantle plume.

Question 8

Hydrothermal activity

Answer 8

The circulation of water through hot volcanic rocks and magmas, producing hot springs and geysers on the surface.

Question 9

Lahar

Answer 9

A torrential mudflow of wet volcanic debris produced when pyroclastic or lava deposits mix with rain or the water of a lake, river, or melting glacier.

Question 10

Large igneous province

Answer 10

A voluminous emplacement of predominantly mafic extrusive and intrusive igneous rock whose origins lie in processes other than “normal” seafloor spreading. LIPs include continental flood basalts, ocean basin flood basalts, and aseismic ridges.

Question 11

Mantle plume

Answer 11

A narrow, cylindrical jet of hot, solid material rising from deep within the mantle and thought to be respon- sible for intraplate volcanism.

Question 12

Rhyolitic lava

Answer 12

The lava that is richest in silica, making it the stickiest and least fluid kind of lava. It erupts at temperatures of only 600° to 800°C. (Compare andesitic lava; basaltic lava.)

Question 13

Shield volcano

Answer 13

A broad, shield-shaped volcano many tens of kilometers in circumference and more than 2 km high built by successive flows of fluid basaltic lava from a central vent.

Question 13

Stratovolcano

Answer 13

A concave-shaped volcano containing alter- nating layers of lava flows and beds of pyroclasts.

Question 14

Tuff

Answer 14

Any volcanic rock lithified from pyroclasts.

Question 15

Volcano

Answer 15

A hill or mountain constructed from the accumula- tion of lava and other erupted materials.