EQ1 2B.3 Flashcards
(15 cards)
How does lithology affect resistance to erosion?
Mineral composition - whether rock is easily broken down by chemical weathering (limestone is, quartz isn’t)
Rock class - Clastic or crystalline
Structure - rocks with fissures/air spaces erode rapidly
Dip of rock strata + juxtaposition of permeable and impermeable rock
What is lithology
Rock type
What are clastic rocks
Made of sediment particles cemented together
What are crystalline rocks
Made of interlocking mineral crystals
Describe igneous rock
-Formed from solidified magma or lava
(eg. granite, basalt)
-Very resistant due to interlocking crystals and have fewer joints and weaknesses
-Slow erosion rates
Describe metamorphic rock
-Formed by heat and pressure changing igneous or sedimentary rocks
(eg. slate, schist, marble)
-Resistant due to crystalline structure
-BUT weaker than igneous because because folds and faults so faster erosion rate
Describe sedimentary rock
-Formed by the compaction and cementation of sediment
(eg. sandstone, limestone, shale)
-Less resistant than metamorphic and igneous rocks as they are clastic, heavily jointed, weak bedding planes
-Usually fast erosion however older sedimentary rock erodes slowly due to more compaction
What is unconsolidated sediment
Sediment that has not yet been cemented to form solid rock
(easily eroded)
What is a complex cliff profile?
Produced where cliffs are composed of strata of differing lithology
What happens when there are alternating permeable and non-permeable strata
Permeable rocks are those that allow water to flow through them bc they are porous/have numerous joints
-Less resistant as large SA for chemical weathering
Impermeable rocks do not allow water to flow through them
Forms complex cliff profile
What role does vegetation play in coastlines
Can stabilise unconsolidated sediment reducing erosion by roots binding sediment together
Inc rate of sediment accumulation by interrupting flow of wind/water, reducing velocity, encourage deposition
What is plant succession
Changing structure of a plant community over time as an area of initially bare sediment is colonised
What are pioneer plants
First plants to colonise freshly deposited sediment
They stabilise sediment, and add organic matter to sand, allows less hardy plants to colonise
Describe a psammosere
(Plant succession on sand dunes)
-Xerophytic plants are adapted to dry conditions
1) Embryo dunes form when seaweed driftwood/litter provides barrier trapping sand
2) Embryo dune grows, colonised by xerophytic pioneer plant e.g. sea couch, saltwort
3) Pioneer plant stabilise sand allowing marram grass to colonise, forms yellow dune
4) Marram grass adds hummus to sand creating soil, grey dune formed
5) Dune above high tide, soil is less saline and has more nutrients allowing non-xerophytic plants to colonise forming climax community e.g. pine, birch
Describe a halosere
Plant succession in salty water
Halophytes are adapted to saline conditions to colonise mud (salt marsh)
1) Fresh water and sea water mix in estuary causing clay particles to stick tg and sink (flocculate)
2) Blue-green algae and gut weed colonise mud
3) Algae binds mud, adds organic matter, traps sediment
4) As the sediment thickens, water depth is reduced, mud is covered by tide for less time
5) Glasswort, cord grass colonise
6) Accumulation of organic matter and sediment raises height of the marsh until it is only covered by spring tides
7) Higher marsh is colonised by less hardy plants e.g. sea lavendar
8) Rainwater washes salt out of the high marsh’s soil, allowing less hardy plants to colonise forming climax community e.g. deciduous oak forest, coniferous pine forest
