8.3 RATES OF EROSION Flashcards
what is unconsolidated sediment?
-material such as sand, gravel, clay and silt that has not been compacted to become sedimentary rock
examples of igneous rocks? (3)
-granite
-basalt
-dolerite
examples of metamorphic rocks? (3)
-slate
-schist
-marble
examples of sedimentary rocks? (3)
-sandstone
-limestone
-shale
what is igneous erosion rate?
VERY SLOW
what is metamorphic erosion rate?
SLOW
what is sedimentary erosion rate?
MODERATE TO FAST
explanation about igneous rocks?
-they are crystalline
-the interlocking crystals make them strong, hard-resistant rock
-granite has few joints to there are limited weaknesses that erosion can exploit
explanation about metamorphic rocks?
-crystalline metamorphic rocks are resistant to erosion
-many have foliation where crystals are orientated in one direction which produces weaknesses
-often folded and heavily fractures
explanation about sedimentary rocks?
-most are clastic and erode faster
-younger rocks tend to be weaker
-rocks with bedding planes (shale) are vulnerable to erosion
do permeable rocks allow water to flow through them?
-yes
do impermeable rocks allow water to flow through them?
-no
what is pore water pressure?
-the pressure water experiences at a particular point below the water table due to the weight of water above it
how can satellite images be useful?
-they show the locations that have rocky shorelines
why are sedimentary rocks more easily eroded than igneous? (3)
-sedimentary consist of loosely packed particles with variable size making them more susceptible to erosion
-sedimentary rocks have bedding planes and jointing which create weakness leading to formation of landforms such as cliffs
-sedimentary rocks have layers of strata, softer layers may erode more quickly than harder
what are three things that protect the coastline?
-sand dunes
-salt marshes
-mangrove swaps
how does vegetation stabilises sediment? (3)
-roots of plants bind sediment together making them harder to erode
-plants growing in sediment provide a protective layer so surface of sediment isn’t directly exposed to moving water and erosion
-plants protect sediment from wind erosion by reducing wind speed at the surface due to friction
many plants that grow in coastal environments are ?
-halophytes
-xerophytes
what can halophytes tolerate?
-salt water
-around their roots
what can xerophytes tolerate?
-dry conditions
-those found on coastal sand dunes where sandy soil remains
what is plant succession?
-changing structure of a plant community over time as an area of bare sediment is colonised by plants
what is a sand dune ecosystem called?
-psammosere
what is a salt marsh ecosystem called?
-halosere
what do the pioneer plants on an embryo dune do? (3)
-stabilise mobile sand with root system
-reduce wind speed allowing more sand to be deposited
-add dead organic matter to sand
how to embryo dunes alter the environment? (4)
-from harsh to an environment other species can tolerate
-so new plant species colonise the area
-creating fore dune
-dunes then grow upward and out to sea
how are dune slacks created?
-periods of wind erosion create low areas within dune systems
what is marram grass?
-example of specialised plants
-tough, long flexible leaves are designed to limit water loss by transpiration
-roots of up to 3m long that tap water below dune surface
why are estuaries ideal for the development of salt marshes?
-they are sheltered from strong waves so sediment can be deposited
-rivers transport a supply of sediment to river mouth
