key words

Question 1

sorting

Answer 1

The degree to which particles are the same size

Question 2

Mechanically formed

Answer 2

sedimentary rocks result from the processes of erosion, transport and deposition of clasts

Question 3

matrix

Answer 3

the background material of small grains in which larger grains occur

Question 4

plasticity

Answer 4

the ability of a material to permanently change shape without fracturing

Question 5

fissile

Answer 5

refers to the tendency of a rock to split into thin layers

Question 6

Ooliths

Answer 6

spherical grains showing concentric banding of carbonate material. These are less than 2mm in diameter

Question 7

micrite

Answer 7

a microcrystalline calcite, a depositional matrix of lime mud

Question 8

cement

Answer 8

the minerals precipitated between grains in sedimentary rocks binding them together

Question 9

pellets

Answer 9

carbonate material excreted by animals. They lack concentric structures and are normally 0.04 to 0.08mm in diameter

Question 10

diagenesis

Answer 10

all the changes that take place in sediments at low temperatures and pressure, at or near to the earth’s surface

Question 11

lithification

Answer 11

the process of changing unconsolidated sediment into rock

Question 12

pressure dissolution

Answer 12

occurs where minerals dissolve as the result of applied pressure because pressure dissolution leads to a reduction of volume of the rock in which it occurs

Question 13

porosity

Answer 13

the volume occupied by spaces in between sedimentary grains. A reduction in porosity squeezes fluid from pore spaces

Question 14

peat

Answer 14

partly decomposed plant remains with high water content

Question 15

coal

Answer 15

a carbon rich rock formed from fossil plant remains

Question 16

permeability

Answer 16

the ability of a rock to allow fluids such as water to pass through it

Question 17

fluvio glacial deposits

Answer 17

sediments produced by glacial melt water streams flowing from a glacier

Question 18

palaeo environment indicator

Answer 18

a sedimentary structure formed in specific environmental conditions in the ancient past

Question 19

palaeo current indicator

Answer 19

a sedimentary structure that allows the direction of an ancient current to be deduced

Question 20

way up structure

Answer 20

allow geologists to work out whether rocks are in their original orientation or whether they have been inverted of folded

Question 21

point bar

Answer 21

deposits of sand or coarser grained sediments on the inside of a meander bend

Question 22

channel lag

Answer 22

coarse grained sediment left in a channel after finer grained particles have been transported away

Question 23

flood plain

Answer 23

flat land adjacent to a river over which it spreads when in flood

Question 24

upward fining

Answer 24

describes a series of layers in which average grain size decreases upwards as energy decreases

Question 25

flash floods

Answer 25

brief but very high energy flows of water over a surface or down a river channel usually caused by heavy rainfall

Question 26

wadis

Answer 26

river channels in a hot desert regions in which flow may occur very occasionally

Question 27

playa lakes

Answer 27

temporary lakes formed by storm run off in deserts having inland drainage

Question 28

evaporites

Answer 28

sedimentary rocks resulting from the evaporation of saline water

Question 29

transgression

Answer 29

occurs where the sea spreads over the land

Question 30

regression

Answer 30

occurs where the sea retreats from the land

Question 31

tests

Answer 31

the hard shell of some planktonic animals

Question 32

bioturbation

Answer 32

the disturbance of sediment by the activities of organisms

Question 33

distributary

Answer 33

a stream channel that takes water away from the main stream channel

Question 34

cyclothems

Answer 34

represent layers repeated due to cyclic sedimentation

Question 35

Clast

Answer 35

a fragment of broken rock produced by mechanical weathering and erosion