2 + A. Rocks and Weathering Key Terms

Question 1

Tectonic Plate

Answer 1

A tectonic plate is a slab of Earth’s Lithosphere.

Question 2

Divergent Plate Boundary

Answer 2

A divergent plate boundary is a plate boundary where two plates are pulled apart due to sub-crustal convection currents causing magma to rise between them forming new crustal material.

Question 3

Conservative Plate Boundary

Answer 3

A conservative plate boundary is a plate boundary where two plates slide past each other at different speeds, causing earthquakes from friction between the two plates.

Question 4

Convergent Plate Boundary (Destructive)

Answer 4

A convergent (destructive) plate boundary is a plate boundary where two plates move together due to sub-crustal convection currents and the denser subducts beneath the less dense and melts. This then causes magma to well up creating pressure under the less dense plate and forming steep composite volcanoes.

Question 5

Convergent Plate Boundary (Collision)

Answer 5

A convergent plate boundary (collision) is a plate boundary where two plates move together due to sub-crustal convection currents and collide. They then compress each other, with the stress forming fold mountains and causing earthquakes

Question 6

Sea Floor Spreading

Answer 6

Sea floor spreading is a geological process where magma rises at mid-oceanic ridges to form new oceanic crust which gradually moves away from the ridge.

Question 7

Subduction

Answer 7

Subduction is the sideways and downwards movement of a denser plate under a less dense plate into the mantle at convergent (destructive) plate boundaries.

Question 8

Fold Mountain Building

Answer 8

Fold mountain building is the emergence / rise of fold mountains from stress and compression between plates at convergent (collision) plate boundaries.

Question 9

Ocean Ridge

Answer 9

An ocean ridge is a seafloor mountain system formed by rising magma at divergent plate boundaries.

Question 10

Ocean Trench

Answer 10

An ocean trench is a long and narrow depression in the seafloor formed as a gap between subducting oceanic plates and obducting continental plates at convergent (destructive) plate boundaries.

Question 11

Volcanic Island Arc

Answer 11

A volcanic arc is a belt of volcanoes formed above a subducting oceanic tectonic plate with the belt arranged in an arc shape as seen from above.

Question 12

Weathering

Answer 12

Weathering describes the processes at or near Earth’s surface that causes rocks and minerals to break down and decay in situ.

Question 13

Physical / Mechanical Weathering

Answer 13

Physical / mechanical weathering describes physical processes that break a rock or mineral into smaller pieces without altering its chemical composition.

Question 14

Chemical Weathering

Answer 14

Chemical weathering is the breakdown of rocks caused by a chemical change within it.

Question 15

Peltier Diagram

Answer 15

The Peltier Diagram is a depiction of the types (physical / chemical) and intensities of weathering that occurr from changes in temperature and rainfall (/ climate).

Question 16

Mass Movement

Answer 16

Mass movement is the transport of weathered rock and sometimes layers of solid rock downslope due to gravity.

Question 17

Erosion

Answer 17

Erosion is the breaking down, picking up and removal of material.

Question 18

Relief

Answer 18

Relief is the variations in elevation of the land’s surface.

Question 19

Freeze-Thaw / Frost Shattering

Answer 19

Freeze-that / frost shattering is a physical weathering process where water enters small cracks in the rock and freezes, expanding by 10%. It melts and refreezes causing the crack to widen until the rock breaks apart.

Question 20

Granular Disintergration

Answer 20

Granular disintergration is a physical weathering process where the different materials inside coarse-grained rocks expand and contract with temperature at different rates.

This causes pressure to build up within the rock until it disintergrates.

Question 21

Block Disintergration

Answer 21

Block disintergration is a physical weathering process where as very jointed rock expands and contracts with heat it breaks up along its joints.

Question 22

Salt Crystallisation

Answer 22

Salt crystallisation is a physical weathering process where saline solutions seep into cracks and joints in the rocks and evaporate, leaving salt crystals behind. These crystals heat up and expand, putting pressure on the rock.

Question 23

Dilation / Pressure Release

Answer 23

Dilation / pressure release is a physical weathering process whereby buried rock is compressed by an overburden. As the overburned erodes, the pressure is released causing fractures to form and expand.

Question 24

Root Wedging

Answer 24

Root wedging is a physical weathering process whereby as plant roots grow they exert pressure on the rock, causing the rock to break up and collapse.

Question 25

Carbonation / Solution

Answer 25

Carbonation is a chemical weathering process whereby carbon dioxide dissolves into rainwater forming carbonic acid. This more acidic rain falls and reacts with calcium carbonate in rocks such as limestone / chalk dissolving them over time.

Question 26

Hydrolysis

Answer 26

Hydrolysis is a chemical weathering process where hydrogen ions in water react with metal cations in minerals in the rock. As this happens, the minerals within a rock are broken up often forming clays.

Question 27

Hydration

Answer 27

Hydration is a chemical weathering process whereby wetting and drying causes the addition / removal of water from molecules of some minerals causing expansion / contraction. This sets up stresses within the rock which weakens it overtime.

Question 28

Bedding Planes

Answer 28

Bedding planes are the lines which separate one line or ‘bed’ of rock from another.

Question 29

Faults

Answer 29

Faults are cracks in the rock where movement has occurred.

Question 30

Joints

Answer 30

Joints are cracks and fissures in the rock caused by cooling, drying or movement.

Question 31

Crystalline

Answer 31

Crystalline is a rock structure created by interlocked crystals e.g. Granite.

Question 32

Cemented

Answer 32

Cemented is a rock structure found in sedimentary rocks with natural cements e.g. sandstones and limestones.

Question 33

Compacted

Answer 33

Compacted is a rock structure found in sedimentary rocks which have been pressed together e.g. mudstones, clays and sometimes sandstones.

Question 34

Unconsolidated

Answer 34

Unconsolidated is a rock ‘structure’ for rocks which have been pushed together or dumped e.g. sand dunes or morraines.