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PLATE TECTONICS & GEOTHERMAL ENERGY
PLATE TECTONICS & GEOTHERMAL ENERGY
Our planet – the Earth – is divided into four layers, which are: the inner core, the outer core, the mantle, the asthenosphere, and the crust.
The inner core is probably solid iron; the outer core is probably very hot rocky material under very high pressure. Because of this great pressure it is in a liquid state. The mantle is less liquid and less hot than the outer core. The outermost part of the mantle is solid.
The asthenosphere is made of the outer most part of the mantle and the crust.
If we want to see what our planet really looks like, we have to drain it completely and strip away all its vegetation. Then it would appear as a cracked shell.
Each plate carries a continent or an ocean basin or both. .
Plates move. They move in different directions so they carry continents and ocean basins with them.
But why do they move? There’s some movement in the mantle due to heat in it.
The boundaries between two plates are called differently based on the movement involved. So:
A divergent boundary is where two plates move in opposite directions.
A convergent boundary is where two plates collide.
A transform boundary is where two plates slide past each other.
When two plates move apart, some mantle material – called magma – rises to fill the gap. North America and Asia are on two plates moving apart. So when magma rises, it gets colder and harder so the ocean basin gets bigger and the two continents move further from each other.
When two plates collide material is destroyed. They are generally a continent-carrying plate and an ocean-basin-carrying one. The plate carrying the ocean basin is heavier and it dives beneath the other plate. This process is called subduction.
The first scientist who first observed the plates movement was Alfred Wegener.
He thought that millions of years ago the continents were joined together. This supercontinent was called Pangaea.
Before him, scholars thought for example that the mountains formed because the Earth was cooling down and so it contracted.
Instead he stated that the mountains formed when two plates collided.
They didn’t believe his theories at first. However he put forward some evidence:
- The same fossilized animals and plants were both on the coast of South America and Africa.
- The shapes of South America and Africa fit perfectly like in a jigsaw puzzle.
- The same rock formations are found both in South America and Africa. In fact the rocks are between 550 and 2000 million years old. Some mountain chains terminate on two different areas.
In the 1950s some scientists found out that ocean basins were spreading. This proved the movement of the continents.
Since the mantle is hot, all this heat represents a precious source of energy. In fact you can find it everywhere beneath the Earth’s surface.Scientists are very interested in the so-called “heat flow”, which is how much heat escapes through the Earth’s surface.Although our planet is full of this energy, it is not always easily accessible. Nonetheless there are some countries which benefit from it. They are the so-called “hot” zones, where the heat flow can be reached at shallow depths, such as in East Africa, Colorado, Iceland, New Mexico.In these areas in fact earthquakes and volcanic eruptions are very common.Geothermal energy can be extracted by drilling holes on the surface.
Needless to say that geothermal energy has lots of advantages. For instance geothermal power plants do not release emissions, they take up less space than other power plants and they are safe. They are reliable and efficient. Maintaining the facility is easy and there’s no waste disposal and transport.
The only disadvantage is that this facility is very expensive.
Geothermal energy is extracted in geothermal power plants, which consist of turbines moved by geothermal steam. They are connected to generators that produce electricity.
There are four types of geothermal power plants:
• Flash Steam Power Plants use water which is turned into steam.
• Binary cycle power plants have reservoirs whose temperature is not very high. So they use that warm water to heat another liquid with a lower boiling temperature than water, called binary liquid. When this liquid boils, it produces steam which make a turbine work.
• Dry steam power plants have reservoirs that produce steam but not water. The steam is piped directly into the plant.
• Hybrid or Enhanced power plants that combine geothermal heat with other sources of energy, such as methane.
Not only can geothermal energy be exploited by means of geothermal power plants. Everybody can use it in their houses. What you need is a heat pump. Heat pumps move the heat from the ground to the house in the winter. In the summer they move the heat from the house into the ground. It exploits the stable (often warm) temperature beneath the ground.
Basically heat pumps collect heat from the ground through a series of pipes, called a loop, buried in the ground and made of high-density polyethylene.
In the heat pump there is a condenser which condensate the Earth’s heat. It then releases it into the house at a higher temperature.
They provide air conditioning, heating, hot water.
In fact some heat pumps have a desuperheater, which provides hot water.
List of sites:
http://www.youtube.com/watch?v=0mWQs1_L3fA
http://geology.com/usgs/geothermal-resources/
http://www.digtheheat.com/News/prosandcons.html
http://www.digtheheat.com/geothermal/geothermal_power_plants.html
http://www.digtheheat.com/geothermal_heatpumps/how_geothermal_heatpumps_work.html
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