2.1) Geosphere Flashcards
1
Q
- Describe the ‘extra-terrestrial impacts’ source for the Earth’s internal heat.
A
- During the Earth’s formation, the kinetic energy contained in colliding extra terrestrial bodies was converted to heat energy upon impact.
2
Q
- Describe the ‘gravitational contraction’ source for the Earth’s internal heat.
A
- In the early stages of formation, the Earth contracted into a smaller volume, resulting in gravitational potential energy (GPE) converting to heat energy.
- At the same time, frictional heat was generated by denser iron and nickel-rich material sinking to the core.
3
Q
- Describe the ‘decay of radioactive elements source for the Earth’s internal heat.
A
- Disintegration of natural radioactive elements in the mantle and crust generates heat energy.
4
Q
- What is heat flow (CONVECTION)?
A
- Convection occurs in both the mantle and core. This is a circulation pattern in which warmer low-density material rises and cooler high-density material sinks.
➞ This transfers heat to the Earth’s surface and drives plate tectonics.
5
Q
- What are ‘plate tectonics’?
A
- The surface of the Earth is covered by seven large rigid plates and a number of smaller plates.
- These plates are all in motion, and not all in the same direction or at the same speed. The movement is caused by convection currents occuring in the underlying mantle.
- Volcanoes, earthquakes and mineral deposits can be found where plates meet and are moving.
➞ This area is known as a ‘plate boundary’. - However, not all of the Earth’s plates move in the same way. They move away from each other (constructive) and towards each other (destructive).
6
Q
- What are CONSTRUCTIVE plate boundaries?
A
- Constructive plate boundaries occur where convection currents in the upper mantle are diverging.
- If this occurs below a continent, a rift valley will form 🏔️
- This type of plate boundary is mostly found in oceans, where the plate type is oceanic on both sides 🌊
- As the plates move apart, the underlying mantle melts, forming magma. The magma rises upwards, erupting through the crust and filling the gap between the plates, creating new oceanic crust 🪨
- A chain of underwater volcanoes is created along the spreading plate margins.
- Hydrothermal vents are often located near constructive plate boundaries 🌋Deep faults form when the oceanic plates move apart. Cold seawater percolates down through faults and is superheated through contact with the magma, before returning to the seafloor via hydrothermal vents.
- The superheated fluids often contain dissolved metallic minerals. As the fluids make contact with the seawater and cool, the dissolved minerals are deposited on the seafloor 🪙
➞ The minerals often accumulate in substantial volumes, which can potentially be exploited.
7
Q
- What are DESTRUCTIVE plate boundaries?
A
- These margins occur where convection currents in the upper mantle are converging, forcing the plates above to move towards each other.
➞ Subduction zones occur where the continental plate and oceanic plate converge 🍽️ - The oceanic plate moves below the continental plate because it is denser, also carrying down oceanic sediments and seawater 🌊
➞ The addition of the sediments and seawater lowers the melting point of the plate materials. - The magma generated from subduction zones has high levels of gas present and is very explosive.
➞ This molten material forces its way up through faults to the surface of the continental plate, erupting as a volcano 🌋 -
Molten material reaching the surface is known as ‘lava’ and cools to form extrusive rock.
➞ Magma that cools and solidifies before reaching the surface forms intrusive rock 🪨 - The magma carries concentrated metallic minerals into the upper crust. Significant metallic mineral deposits are often found near ancient plate boundaries 🪙
- As the oceanic plate moves below the continental plate, a deep ocean trench forms at the junction.
➞ Subduction also causes crumpling along the edge of the continental plate, forming fold mountain chains 🏔️ - Earthquakes at this boundary can be of high magnitude due to the release of frictional pressure that builds up between the two plates 🫨
8
Q
- What is the FORMATION of bauxite ore deposits?
A
- Bauxite:
➞ is an ore rich in aluminium oxide and is found in extractable quantities in areas associated with subduction zones (DESTRUCTIVE) - Bauxite forms in tropical areas around the Equator, where high temperatures and abundant rainfall result in extreme chemical weathering of rock.
- As water percolates through the soil in the hot, humid climate, nutrients dissolve and leach downwards.
- The soil that remains, known as laterite, can be rich in aluminium oxides and form rich ore deposits near the surface.
9
Q
- What are the environmental impacts of MINING of bauxite ore deposits?
A
The majority of world bauxite production is from surface means, extracted by open cast mining.
IMPACTS:
1. Landscape changes through removal of timber, vegetation, rock and soil with associated impacts on ecosystems and biodiversity 🏔️
2. Control of erosion and runoff from the mine 🪨
3. Mining disturbs the movement, quality and distribution of water in the area 🌊
4. Disposal of the overburden, tailings and other waste 🗑️
5. Dust, noise and emissions caused by mining operations and transport 💨
10
Q
- What are the environmental impacts of PROCESSING of bauxite ore deposits?
A
IMPACTS:
1. Smelting and processing require enormous inputs of electricty, water and resources, such that power plants are often constructed nearby ⚡
2. Smelting and processing releases high levels of greenhouse gases, particulates and other harmful substances 🔥
3. Bauxite is often transported long distances to countries with processing plants 🚛
11
Q
- What is geothermal energy?
A
- Geothermal energy:
➞ is a carbon-free, renewable and sustainable form of energy which uses heat from within the Earth to produce hot water and electricity. - Traditionally, geothermal energy has been restricted to regions near to plate boundaries, where the crust is thinner or at areas where plumes create geothermal hotspots (i.e., Hawaii and Yellowstone in central USA).
12
Q
- What is the ‘geothermal gradient?
A
- Geothermal gradient:
➞ is the amount that the Earth’s temperature increases with depth. It indicates heat flowing from the Earth’s warm interior to its surface. - On average, the temperature increases by 25℃ for every kilometre of depth. This difference in temperatures drives the flow of geothermal energy and allows humans to use this energy for heating and electricity generation.
- There are a number of places on the planet where the temperature changes quite a bit faster, and those locations are almost always where geothermal energy is the most viable (e.g., Japan, New Zealand and Iceland)
13
Q
- State the two main sources of geothermal energy.
A
- Groundwater: Steam and hot water
- Ground source: Hot rocks
14
Q
- What is the PROCESS of geothermal energy?
A
- Generally, two or more holes are drilled down to the region of hot rocks and water is pumped down one.
- This water comes back up the other hole at a high temperature, usually much hotter than 1000℃.
- At this temperature, water will remain as a liquid, providing it is under pressure.
- When it reaches the surface and the pressure is decreased, it “flashes” into steam, which we can use to heat houses, or to turn turbines and generate electricity.
15
Q
- What are the ADVANTAGES of geothermal energy?
A
- Environmentally friendly compared to gas or oil furnaces (no combustion) 🔥
- Geothermal energy is a renewable resource ♻️
- Suitable for the smallest of houses to the largest commercial spaces 🏬
- Mostly underground for a minimal landscape footprint 🏔️
- Efficient (300% - 500% compared to 90% of the best furnaces) ✅
