Practical 2 definitions

Question 1

Lithosphere

Answer 1

Rigid, rocky outer layer of the Earth, consisting of the crust and the solid outermost layer of the upper mantle. It extends to a depth of about 60 mi (100 km).

Question 2

Asthenosphere

Answer 2

The highly viscous, mechanically weak and ductilely deforming region of the upper mantle of the Earth. It lies below the lithosphere, at depths between approximately 80 and 200 km (50 and 120 miles) below the surface.

Question 3

Continental Crust

Answer 3

Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the continents and the areas of shallow seabed close to their shores. The continental crust consists of various layers, with a bulk composition that is intermediate (SiO2 wt% = 60.6)

Question 4

Oceanic crust

Answer 4

Oceanic crust, the outermost layer of Earth’s lithosphere that is found under the oceans and formed at spreading centres on oceanic ridges, which occur at divergent plate boundaries.
The oceanic crust consists of a volcanic lava rock called basalt. Basaltic rocks of the ocean plates are much denser and heavier than the granitic rock of the continental plates. Because of this the continents ride on the denser oceanic plates.

Question 5

Solidus

Answer 5

a solidus is the set of temperatures below which a substance is completely solid or crystallized. The solidus defines the temperature at which a substance begins to melt, but not necessarily when the substance is completely melted.

Question 6

Liquidus

Answer 6

the liquidus line represents the locus of temperatures above which the substance exhibits the behavior of a stable liquid.

Question 7

Partial melting

Answer 7

Partial melting occurs when only a portion of a solid is melted. For mixed substances, such as a rock containing several different minerals or a mineral that displays solid solution, this melt can be different from the bulk composition of the solid.

Question 8

decompression melting

Answer 8

The process of decompression melting involves the upward movement of the earth’s mantle to an area of lower pressure. The reduction in overlying pressure enables the rock to melt, leading to magma formation.

Question 9

Geotherm

Answer 9

The definition of geotherm in the dictionary is a line or surface within or on the earth connecting points of equal temperature

Question 10

Adiabatic geothermal gradient

Answer 10

the rate at which the temperature of an ascending or descending body of air is changed by adiabatic expansion or compression, being about 1.6° F for each 300 feet of change of height

Question 11

Basalt

Answer 11

Basalt is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill.

Question 12

Gabbro

Answer 12

Gabbro is a dense, mafic intrusive rock. It generally occurs as batholiths and laccoliths and is often found along mid-ocean ridges or in ancient mountains composed of compressed and uplifted oceanic crust. Gabbro is the plutonic equivalent of basalt

Question 13

Moho

Answer 13

The Mohorovicic Discontinuity, or “Moho,” is the boundary between the crust and the mantle. The red line in the diagram shows its location. In geology the word “discontinuity” is used for a surface at which seismic waves change velocity.

Question 14

Hotspot Track

Answer 14

In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. A hotspot track results if such a region is moving relative to the mantle.

Question 15

D” Layer

Answer 15

Lowermost portion of the mantle which sits above the molten (iron-rich) outer cor

Question 16

410 km discontinuity

Answer 16

The discontinuity at the depth range around 410 km (the 410) is a dominant feature of most upper mantle models. The 410 characterizes the beginning of the mantle transition zone.

Question 17

520 km discontinuity

Answer 17

Seismic discontinuity around a depth of 520 km, A surface at which velocities of seismic waves change abruptly. A boundary between seismic layers of the earth.

Question 18

670 km discontinuity

Answer 18

The seismic discontinuity at a depth of approximately 660 km (the 660) as the boundary between upper and lower mantle plays an important role in the dynamic state of the Earth’s interior.

Question 19

Peridotite

Answer 19

Peridotite is a dense, coarse-grained igneous rock consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. … Peridotite is the dominant rock of the upper part of the Earth’s mantle.

Question 20

Pyrolite

Answer 20

Pyrolite, rock consisting of about three parts peridotite and one part basalt. The name was coined to explain the chemical and mineralogic composition of the upper mantle of the Earth. … Accordingly, it is reasonable to assume that to a first approximation these abundances are applicable to the entire mantle.

Question 21

Lhertzolite

Answer 21

The most common form of peridotite, mostly composed of olivine, orthopyroxene (commonly enstatite), and clinopyroxene (diopside), and have relatively high proportions of basaltic ingredients (garnet and clinopyroxene).

Question 22

MORB

Answer 22

A type of tholeiitic basalt, erupted from mid-ocean-ridge constructive-plate margins; it is one of the most abundant of all rocks and covers much of the Earth’s surface

Question 23

mafic

Answer 23

Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite.

Question 24

Andesite

Answer 24

An extrusive igneous volcanic rock of intermediate composition. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic.

Question 25

Mid ocean ridges

Answer 25

Explorer Ridge
1. Located in the west of Vancouver Island, British Columbia, Canada.
2. It is divergent tectonic plate boundary between Vancouver Island, British Columbia, Canada.
Gorda Ridge
1. Located at the northern coast of California and southern Oregon.
2. It is tectonic spreading centre broken into three segments- the northern ridge, central ridge and the southern ridge.
Juan de Fuca Ridge
1. Located at the off coast of the Pacific Northwest region of North America.

2. It is a mid-ocean spreading centre and divergent plate boundary.
3. It separates the Pacific Plate to the west and the Juan de Fuca Plate to the east.
   American-Antarctic Ridge
4. Located between the South America and Antarctica
5. It is the tectonic spreading centre between the South American Plate and the Antarctic Plate.
   Chile Rise
6. Located in the Peru-Chile Trench
7. It is a tectonic divergent plate boundary between the Nazca and Antarctic Plates

Question 26

Hot spot

Answer 26

Caribbean Islands, Atlantic Forest, Cerrado, Chilean Winter Rainfall- Valdivian Forests, Tumbes-Chocó-Magdalena, Tropical Andes

Question 27

Four major elements earth

Answer 27

Oxygen, Silicon, Aluminum, Iron