Mock revision 2B.3 Rates of recession and Stability Flashcards
How is sedimentary rock formed?
Compression and compaction of deposited sediment over millions of years.
How is igneous rock formed?
Slowly cooled magma beneath the earth’s surface.
How is metamorphic rock formed?
Recrystallisation of sedimentary and igenous rocks through heat and pressure.
Name an example of an sedimentary rock
Carboniferous limestone.
Name 2 examples of an igneous rock
Granite and basalt.
Name 2 examples of a metamorphic rock
Slate and marble.
What is the structure of sedimentary rock?
Clastic.
What is the structure of igenous rock?
Crystalline composing of interlocking crystals.
What is the structure of metamorphic rock?
Crystalline composing of interlocking crystals.
What are the recession rates of sedimentary rocks?
0.5 to 10cm per year.
What are the recession rates of igneous rocks?
Less than 0.1cm per year.
What are the recession rates of metamorphic rocks?
0.1 to 0.3cm per year.
Why are metamorphic rocks weaker than igneous rocks?
Crystals are orientated in the same direction (foliation) making them weaker than interlocking crystals of igneous.
Why do igneous rocks have few weaknesses?
Strong internal cohesion/
What weaknesses do metamorphic rocks possess?
Folds and faults due to folding.
Name 3 examples of unconsolidated rock
Fluvial alluvium
Glacial boulder clay
Aeolian loess
What are the recession rates of the unconsolidated rocks along the Holderness coast?
2 to 10m per year.
Name 3 roles played by vegetation
- Leaves slow transporting medium, decreasing energy and encouraging deposition
- Roots bind unconsolidated sediment, decreasing erosion
- Add organic matter to soil, increasing fertility, encouraging plant succession.
Give the alternative name for sand dunes
Psammosere.
What is the pioneer species of sand dunes and what do they do?
Sea twitch (bind and trap) - colonising bare sand (0.8% organic matter, soil depth 0.5cm, and pH 8.5).
What type of species are sea twitch?
Xerophytic, can stand dry, hot conditions and constant inundation by sand.
What do sea twitch form?
Embryo dunes.
What do embryo dunes do?
Roots stabilise, leaves encourage deposition when vegetation dies, and increase organic matter content so less tolerant species develop (fore dunes).
What do fore dunes do?
Grow and build out of high tide - maram grass start to outcompete pioneer species.
What does maram grass posses?
Long tap roots of 3m+.
Long leaves grow at 1m per year.
What does the maram grass form?
Yellow dunes.
What do yellow dunes do?
Continue succession through seral stages, decreasing erosion and increasing quantity of less tolerant species.
What does the sand dune succession end with?
Climax community of a pine woodland - very stable and decrease flooding.
What is the alternate name for a salt marsh?
Halosere.
Where do salt marshes form at?
Mouth of rivers, often behind spits and can form on cuspate forelands.
How does the development of salt marsh start?
Fine muds and silts create mudflats. Pioneer species such as algae and eel grass colonise, so they can withstand 11-12 hour indundation by saltwater at high tide (halophytic).
What does the eel grass algae do?
Reduce the velocity of the tidal ebb by allowing sediment to be deposited and build up mud flat area.
What occurs in the next seral stage after a mud flat is built up?
Spartinia form with a more developed root system, inceasing stability and build above highest tidal range, so the growing conditions improve (rainwater washes away salt).
What is the climax communiity of a salt marsh?
Oak woodland.
Where do mangrove trees form?
30 degrees north and south.
What do mangroves do?
Dissipate wave energy, reducing wave height by 50%.
Why do mangroves reduce energy and erosion?
Roots bind to sediment.
