Geology Flashcards
What happens at a Convergent Oceanic/Oceanic Plate Margin?
Deep Ocean Trench at Subduction Zone
Andesitic Volcanic Arc Caused by rising magma as crust melts below it
Benioff Zone Causing Shallow and Deep Earthquakes
Faster moving one subducts below slower one
Destructive as moving towards one another
Regional/Contact Metamorphism
Granite Batholith and Thrust Faults
What happens at an Divergent Oceanic/Oceanic Plate Margin?
Mountain Ridge-Mid-Atlantic Ridge Basalt/Mafic Materials Basaltic Shield Volcanoes Transform Faults and Shallow Earthquakes Magnetic Stripes Constructive as moving away from one another Rift Valleys
What happens at an Convergent Continental/Oceanic Plate Margin?
Oceanic Plate subducted below Continental Plate as Oceanic is more dense
What happens at an Convergent Continental/ Continental Plate Margin?
No Volcanoes Big Mountains Partial Melting of Deep Continental Crust Batholiths Silicic
Why do plates/rocks melt?
Temperature has increased
Pressure decreased
Saturated in water
What is the difference between acidic, mafic, medium and ultrabasic igneous rocks?
Acidic-More than 66% quartz content
Medium-66%-52% quartz content
Basic-52-44% quartz content
Ultrabasic-Less than 44% quartz content
The more quartz in a magma…
The more explosive the volcanic eruptions because the magma is sticky and viscous
What is the lithosphere?
The crust and the upper most solid mantle
Plates are made up of the lithosphere cracked into smaller pieces
What is the asthenosphere?
The magma below the lithosphere which allows for movement of the plates over lower part of the mantle
What happens at Conservative Plate Margins?
Plates are sliding past one another
Large Scale Fault Lines
Shallow Earthquakes
How might you support the land on either side of a road cutting?
Retaining Wall Bolts Anchor Gabions Drains Fabric at Top
Tell me about V-Shaped Valleys
Formed in upland rivers, where they vertically erode the landscape to get to base/sea-level
Wider at top because material which falls of side of valley is taken away and eroded via abrasion and attrition
In places where the rocks are different hardness’s waterfalls will be formed, which may move backwards through the valley
Tell me about rivers in Lowland Areas
Form flood-plains, wide areas of land where the river meanders back and forth at a slow rate due to angle not so steep as nearer sea level
Tell me about U-Shaped Valleys
Formed by glacial erosion, where the ice cuts straight through the valley, not worrying about the path of the river, following a direct route down the hill
The ice plucks boulders and unconsolidated material from the valley floor, which gets dragged along with the glacier further eroding the base
Tell me about Super-Imposed Drainage
Rivers don’t follow underlying geology
Rivers form on overlying layer of rock which is then eroded away
Tell me about Plateaus
Flat layers of either igneous or sedimentary rocks which have a shallow dip and have a top layer which is harder than the surrounding rock form hills or mountains with very flat tops
Tell me about Scarps and Vales
Tilted beds of differing hardness in rocks lead to scarps or peaks being formed with vales in between
The sharply dipping side of these hills is the scarp slope and the shallower one is the dip slope
Tell me about Ridges
Long and narrow hills formed by rocks of different hardness’s (often dykes) being eroded slower than the surrounding rocks
Tell me about a Fault Scarp
Faults happen at rocks of different hardness and the fault marks the place the different rocks meet
The soft rock is the low ground, and the hard rock is the high ground
What is the difference between a concordant and discordant coast?
Concordant-Same rock facing the sea
Discordant-Different rocks facing the sea, so bays and headlands/high cliffs are formed due to softer and harder rocks
Tell me about Graptolites
Made up of stipes (body parts) and thecas (spikes)
As time went on and they evolved there became less stipes, their theca point outwards instead of inwards and theca become more complex, from straight lines to hooks
Shape of Stipe: Pendant (hanging down), to Horizontal, to Reclined (V-Shaped with theca on inside) to Scandent (standing up in straight line)
Tell me about ammonoids
Made up of the Body Chamber (the large part on the outside), then lots of small Chambers with Septa between them, circling inwards
Where the septa meets the shell there are suture lines
These line have become more complicated over time
The top bends are saddles and the bottom parts are lobes (like peaks and troughs in waves)
How are fossils formed?
Buried (often at bottom of sea) and then compacted
Oxygen, Hydrogen and Nitrogen leave body and soft body parts disintegrate
Hard parts are left, leaving a mould in rock when they dissolve
Then minerals come in mould to make perfect shape of old animal
You can also get dinosaur footprints fossilised
Which type of rock does Radiometric Dating not work and why?
Sedimentary rock, for it is fragments of other rocks so any kind of dating could be wrong
Having a certain element that has decayed in sedimentary rock may have done the decaying in another rock, so we can never be sure
What is a bed?
A single unbroken episode of sedimentary accumulation
What are bedding planes?
Where there has been a changed in sediment
What are laminations?
Thin layers less than 1cm thick
How is graded bedding formed?
Where rock has been dumped from a height
Tell me about cross-bedding
Formed in 2 ways, and is when there is lines across the beds, where the direction of the lines (going from top to bottom) is the direction of movement
Desert Dunes-Where sand carries small particles up the shallow side of the dune and then falls down the other (steeper) side and is collected there
River Beds-Current carries small particles which make lines
Difference between Catastrophism and Gradualism
Catastrophism is a natural disaster where things happen quickly and dramatically
Gradualism is a very slow and gradual change in Geology
From centre to outmost layer, list the structures of the Earth or layers of the Earth and tell me about them
Inner Core-Dense, hot and pressurized
Outer Core-Less dense
Both Cores-Causes Earths Magnetism and Spin due to Nickel and Iron content
Mantle-Causes Tectonic Plate Movement, largest layer
Crust-Thin and Solid
How is Granite Chemically Weathered?
Orthoclase Feldspar in Granite is broken down by hot
water leaving Mica and Quartz. Orthoclase Feldspar becomes China Clay or Kaolin which is used to make china and shiny magazines
How is Limestone made?
Sea Shells release their Calcium Carbonate which lithifies to form Limestone
Made in warm, brackish, shallow and still bodies of water, like lagoons
What is Corrosion?
Where rock fragments erode bedrock
What is Attrition?
Where rock fragments hit against each other
What is Abrasion?
Both Corrosion and Attrition
What is Hydraulic Action?
Where air is trapped in holes in rocks and squeezed by water
What is plucking?
Where ice freezes to bedrock and plucks away unconsolidated material like boulders
What is a load when it is in solution?
The load is dissolved in water
What is a load when it is in suspension?
Load is carried in main body of water and air
What is happening to a load when it is experiencing saltation?
Load is bounced along, sending next one into motion
What is happening to a load when it is experiencing traction?
Load is rolled or dragged along an eroded surface
What are the 5 Agents of Erosion?
Wind Rivers Gravity Sea Ice James Bond
What is the difference between breccia and conglomerate and how are they formed?
Conglomerate has rounded rocks in it, while in breccia they are more jagged
Formed when rocks are deposited then squeezed together by pressure
Name the 4 types of Petroleum Traps
Anticline Trap
Fault Trap
Salt Dome Trap
Unconformity Trap
What is infiltration in hydrogeology?
When water enters and is absorbed by the soil
What is percolation in hydrogeology?
When water is absorbed by the rock
What is groundwater flow in hydrogeology?
When water in rocks moves towards and enters a sea or river