Intro To Geology Test 2

What is partial melting?

The process by which only part of an original rock melts to produce magma.

What is mafic magma?

Magmas or igneous rocks that are relatively poor in silica and rich in iron and magnesium.

What is felsic magma?

Magma or igneous rock that is rich in silica.

What is assimilation?

The incorporation of chemicals dissolved from the wall rocks of the chamber or from blocks that detached from the wall and sank into the magma.

What are the types of magma?

1. Felsic: more than 66% Si.

2. Intermediate: 52-66%.

3. Mafic: 45%-52% Si.

4. Ultramafic: 38%-45%.

What is viscosity?

Resistance to flow.

What are some key details in mafic magma?

1. Low viscosity.

2. Low silica content.

Lava

1. Can move up to 30 km per hour.

2. Flows traced up to 500 km from the source in WA.

3. Smooth flows.

What are some key details in intermediate magma?

1. Higher viscosity.

2. Higher silica content.

Lava

1. Moves 1-5 m a day.

2. Flows are 10 km long.

3. Blocky flows.

What are some key details in felsic magma?

1. Highest viscosity.

2. Highest silica content.

Felsic Lava

1. Flows are short 300m.

What are the 3 ways partial or complete melting occurs?

1. Decompression.

2. Addition of Volatiles.

3. Heat Transfer.

What is decompression melting?

Upwelling from deeper in the earth creates a reduction in pressure and therefore melting.

What is a geotherm?

The change in temperature with depth inside the Earth.

What is solidus

Conditions where rock begins to melt.

What is liquidus?

Conditions at which rock completely melts.

What are volatiles?

Chemicals that evaporate easily lowering the melting temperature of minerals.

Why does magma rise?

Because it is hot and less dense therefore buoyant.

What is intrusive?

Magma underground.

What is extrusive?

Lava above the ground.

What is a country rock?

The existing rock in a region.

What are discordant intrusions?

Intrusions that cut the country rock.

What are concordant intrusions?

Intrusions that follow the country rock layering.

What are some examples of a discordant intrusion?

1. Volcanic pipe.

2. Dike.

3. Batholith.

What are some examples of a concordant intrusion?

1. Sill.

2. Laccolith.

What is a volcanic pipe?

A deep, narrow cone of solidified magma (described as “carrot-shaped”).

What is a volcanic neck?

Eroded volcanic vent.

What is a dike?

A tabular intrusion that cuts across preexisting layering in the country rock.

What is a batholith?

A large body of intrusive igneous rock believed to have crystallized at a considerable depth below the earth’s surface.

What is a sill?

A tabular intrusion that injects parallel to layering.

What is a laccolith?

Intrusions between layering that dome upward creating a blister shaped intrusion.

What is xenolith?

A rock fragment that becomes enveloped in a larger rock.

What are the 3 types of material released from volcanoes that extrusive rocks form?

1. Gases.

2. Pyroclastic Material.

3. Lavas.

What are pyroclastics?

Material/rock fragments ejected into the air from a volcano.

What are the types of volcanoes?

1. Stratovolcanoes.

2. Shield.

3. Super volcanoes.

4. Fissure Flows.

5. Flood Basalts.

What are the two main classes of volcanoes?

1. Stratovolcanoes.

2. Shield.

What is a stratovolcano?

Large volcanoes that consist of interweaved layers of lava and pyroclastic debris.

What are some distinctive features for a stratovolcano?

1. Forms a large mound above the vent.

2. Lava flows are more Felsic creating slow moving thus form angular blocks.

What is a shield volcano?

A subaerial volcano with a broad, gentle dome formed either from low-viscosity Mafic lava or from large pyroclastic sheets.

What are some distinctive features of a shield volcano?

1. Mafic magma.

2. 90% of the volcano is lava.

3. Pyroclastic are not explosive.

4. Have large gentle sloping sides.

What is a super volcano?

A volcano that has had an eruption with a Volcanic Explosivity Index (VEI) of 8, the largest recorded value on the index.

What are fissure eruptions?

A linear volcanic vent through which lava erupts, usually without any explosive activity. Can occur as a secondary vent on a volcano OR on its own.

What are continental flood-basalt eruptions?

Continental flood-basalt eruptions have been the largest eruptions of lava on Earth.

What are some distinctive features of Columbia River Basalts?

1. Flows originated from 3 major fracture flows.

2. Plateau of 164,000 km^2.

3. The fronts of the flows were several stories thick.

4. 3 mph.

What is a volcanic vent?

An opening exposed on the earth’s surface where volcanic material is emitted.

What is the central vent?

The main volcanic vent connected to the magma.

What is a flank vent?

A small opening on the side of an active volcano that can serve as an exit for gas and lava.

What are craters?

Small circular depressions created primarily by explosive excavation of rock during eruptions.

What are calderas?

Cauldron-like volcanic feature on large central volcanoes.

What is a lava dome?

A roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano.

What is a lava fountain?

A jet of lava into the air by the rapid formation and expansion of gas bubbles in the molten rock.

What is a spatter cone?

Low, steep-sided hill or mound that consists of welded lava fragments.

What is a cinder cone?

Small, steep-sided volcanic cones built of loose pyroclastic fragments.

What is a lava tube?

An insulated, tunnel like conduit within a flow where lava moves. As the crust cools it insulates the interior of the flow.

What is a pahoehoe flow?

Smooth, glassy, rope-like ridges of basalt-created when lava flows are warm and pasty.

What is a pillow lava?

Thick sequences of discontinuous pillow-shaped masses typically formed underwater.

What is an A’a’ flow?

A jumble of sharp, angular fragments of rock-created when the surface layer of lava freezes and then gets broken up.

What is columnar jointing?

Intersecting fractures form a regular array of polygonal prisms created when lava contracts as it cools.

What is a mafic rock?

A rock with low silica and high Iron and Magnesium content, typically dark colored.

What is a felsic rock?

A rock with high silica content, typically light colored.

What is an aphanitic texture?

An igneous texture in igneous rock in which individual grains are too small to be seen without magnification.

What is phaneritic texture?

A coarse grain texture in igneous rocks in which mineral grains are easily visible without magnification.

What is an extrusive rock created by?

Created by the freezing of Lava above the ground.

What is an intrusive rock created by?

Created by the freezing of magma.

What is a porphyry rock?

An igneous rock of markedly different sizes.

What is a vesicle?

A small hole or cavity formed by gas trapped in cooling lava.

What is a rhyolite?

An extrusive igneous rock with very high silica content. Usually pink or gray in color. Grains so small that they are difficult to observe without a hand lens.

What is an andesite?

A fine-grained, extrusive igneous rock, usually light to dark gray in color. They have small crystals that cannot be seen without the use of a magnifying device.

What is a basalt rock?

A mafic, dark-colored, fine-grained, igneous rock. Typically extrusive. Underlines more of the earth’s surface than any other rock type.

What is a scoria rock?

Dark-colored, mafic, igneous rock with abundant vesicles. Color can be black or dark gray to deep reddish brown.

What is a pumic rock?

A light-colored, felsic, extremely porous, igneous rock that forms during explosive volcanic eruptions.

What is an obsidian rock?

An igneous rock created when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure.

What is a tuff?

An igneous rock that forms from the products of an explosive volcanic eruption that are compacted and cemented into a rock.

What is a dunite rock?

Coarse-grained, dark-colored, ultramafic igneous rock composed primarily of olivine.

What are gabbro rocks?

Coarse-grained, mafic, intrusive igneous rocks.

What is a diorite rock?

An intrusive igneous rock composed principally of the silicate minerals.

What is a granite rock?

A light-colored igneous rock with grains huge enough to be visible with the unaided eye.

What is a pegmatite rock?

A coarse-grained igneous rock formed in dikes.

What is physical weathering?

The process in which intact rock breaks into unconnected grains or chunks.

What is unloading?

The release of confining pressure associated with removing overlying material.

What is an abrasion?

A physical process that occurs when particles of rock are worn away by friction.

What is biologic physical weathering?

Plant roots and burrowing organisms force the rock apart.

What is chemical weathering?

The process in which chemical reactions alter or destroy minerals when rock comes in contact with water solutions or air.

What is biogeochemical weathering?

Living organisms produce chemicals used to break down rock.

What is a sediment?

Loose fragments of rocks or minerals broken off bedrock, mineral crystals that precipitate directly out of water, and shells or shell fragments.

What is differential weathering?

Specific minerals and rocks weather at different rates.

What is velocity?

Distance over a given time.

What are the 3 types of bedding?

1. Well sorted.

2. Poorly sorted.

3. Graded.

What is lithification?

The process of converting of loose sediments into solid sedimentary rocks.

What is compaction?

The space between mineral grains gets smaller without changing their structure.

What are the two ways to identify a sedimentary rock?

1. Clastic- particle size.

2. Chemistry- chemically formed.

What are clastic rocks based on?

Clastic rocks are based on grain size of rock particles.

What is a breccia rock?

A rock formed from angular gravel and boulder-sized clasts cemented together in a matrix.

What is a conglomerate rock?

Sedimentary rock that is composed of a substantial fraction of rounded to sub-angular gravel-size clasts.

What is a sandstone rock?

Composed mainly of sand-sized minerals or rock grains.

What is a siltstone rock?

Rock composed of silt size particles.

What is a shale rock?

Rock composed of clay and silt size particles.