Rocks and Weathering Flashcards
What shape does the earth resemble due to its spin?
A geode
The earth is flatter at the poles and bulges at the equator.
Which layer of the Earth is the thinnest?
Crust
The crust consists of two types: continental and oceanic.
What is the thickest layer of the Earth?
Mantle
The mantle is composed of molten rock.
What is the upper layer of the mantle called?
Lithosphere
The lithosphere is made up of solid crust and mantle and is broken into tectonic plates.
What separates the colder, more rigid rocks from the hotter, more plastic rocks in the mantle?
Asthenosphere
The asthenosphere is a liquid layer of the mantle that tectonic plates float on.
What are the main components of the outer core?
Liquid metals: iron and nickel
The outer core is in a liquid state.
What is the state of the inner core and why?
Solid due to pressure
The inner core is the hottest layer of the Earth.
What is the thickness range of oceanic crust?
6-10 km
Oceanic crust is thinner than continental crust.
What is the age of oceanic crust?
Less than 200 million years
Oceanic crust is younger than continental crust.
What is the average density of oceanic crust?
3.0 g/cm³
Oceanic crust is denser than continental crust.
What is the composition of oceanic crust?
Basalt, silicon, magnesium, oxygen
Oceanic crust has a heavier composition.
What is the thickness range of continental crust?
30-70 km
Continental crust is thicker than oceanic crust.
What is the age of continental crust?
Over 1,500 million years
Continental crust is significantly older than oceanic crust.
What is the average density of continental crust?
2.6 g/cm³
Continental crust is less dense than oceanic crust.
What is the primary composition of continental crust?
Mainly granite, silicon, aluminium, and oxygen
Continental crust has a lighter composition compared to oceanic crust.
True or False: Oceanic plates are denser than continental plates.
True
The density of oceanic plates increases due to the weight of the ocean compressing it.
What are Constructive (divergent) plate margins?
Where two plates separate. This can occur in either oceanic areas or continental areas. O-O C-C
What are Destructive (convergent) plate margins?
where two plates collide
What are the 3 possible types of convergence?
- Oceanic meets continental
- Oceanic meets oceanic
- Continental meets continental (collision)
What are Conservative (transform) plate margins?
where 2 plates slide past one another.
What is a mid-ocean ridge?
Oceanic divergence leads to sea-floor spreading along either side of submarine mountain ridges thousands of kilometres long such as the Mid-Atlantic Ridge
What is weathering?
The decomposition/decay and disintegration of rocks in situ
What are the two main types of weathering?
physical/mechanical and chemical
What does the efficiency of weathering processes depend on?
The interaction between climate, the properties of the rock and local factors such as relief.
What is disintegration?
Disintegration occurs from physical (mechanical) weathering- breaking into smaller, angular fragments of the same type, resulting in scree.
What is decomposition?
Decomposition affects of chemical weathering and changes the rocks substance, for example creating kaolinite (China clay) from granite
What is weathering caused by?
changes in atmospheric conditions (such as temperature, moisture and wind) acting on a stationary object.
What is regolith?
Loose material (soil + weathered rock) in a layer on top of solid bedrock.
What do mass movements include?
any large-scale movement of the Earth’s surface that are not accompanied by an erosive agent such as a river, glacier or ocean wave.
What is mass movement?
The downslope movement of rock and weathered debris by gravity alone.
How can mass movements be classified?
- Speed of movement
- Water content
- Type of movement (heaves, flows, slides or falls)
- Material involved
e.g.
- Very slow movements, such as soil creep
- Fast movements, such as avalanches
- Dry movement, such as rockfalls
- Fluid movements, such as mudflows.
What is sheer stress?
The force trying to move the mass down
What is sheer stength?
The force trying to hold the mass on the slope.
When does a slope ‘fail’?
when it is too steep and unstable for existing materials and conditions or when shear strength < shear stress
What are the most important factors that determine mass movement?
gravity, slope angle and water.
Give examples of heaves
- Soil creep
- Talus creep
- Solifluction
Give examples of flows
- Mudflow/ lahars
- Earthflow
Give examples of slides
- Landslide
- Rockslide
- Rotational slide
Give an examples of a fall
Rock fall
What is soil creep?
the movement of soil particles
What is talus creep?
The slow movement of fragments on a scree slope
What is solifluction?
Found in areas of permafrost, where summer thawing leads to waterlogged conditions and accelerated creep.
When does surface run-off occur?
When the soil’s infiltration capacity is exceeded
What is sheet wash erosion?
the un-channelled flow of water over a soil surface
What are rills?
Relatively shallow channels (usually less than tens of cm deep) that are formed by water eroding channels on slopes and are common in agricultural areas following the removal of vegetation during harvest season.
What is rainsplash erosion?
Soils are knocked into the air by the raindrop impact
How do gulleys form?
if water becomes concentrated in rills for longer periods they may widen and deepen to form channels known as gullies.
