Human Interaction with the rock cycle

The rock cycle

explains the repeated creation and destruction of rocks and minerals. It shows how the three main groups igneous, sedimentary, and metamorphic are formed.

How humans interact with the rock cycle

Humans interact with the rock cycle by accessing geothermal energy while igneous or metamorphic rocks form. This happens in about 20 countries worldwide including Iceland, Kenya, and New Zealand.

Geothermal energy uses heat from hot igneous rocks to heat water and generate steam to produce electricity.

geothermal energy

Geothermal energy is energy that has been obtained from the natural heat that is coming up from the core through the mantle and into the crust.

In Iceland an active volcanic zone stretches through the country as it is on the Mid Atlantic ridge where the Eurasian and North American plates are pulled apart and contains over 130 active volcanoes so the heat is close to the earth's surface.

geothermal gradient

Geothermal energy is usually developed close to plate boundaries especially where the crust is thin. Temperatures of crustal rocks naturally increases with depth by about 25 degrees Celsius per kilometre.

How water is heated during the rock cycle

During the rock cycle magma is pushed up into the crust which form igneous rocks. (As part of the rock cycle minerals in other rocks close to the magma intrusion may recrystalise to form metamorphic rocks).

The temperature of this magma is up to 1300 degrees Celsius and as a result the temperature of the rocks in the crust rises. The rocks may take hundreds of thousands of years to cool down.

Water seeps down through cracks and faults in rocks and the water absorbs heat from heated rocks and the magma. In areas of volcanic activity such as Iceland this water is superheated under pressure from the surrounding rocks to temperatures of normally 200 degrees but even up to 350 degrees Celsius.

An underground reservoir of superheated water may form. At times, the superheated water escapes to the surface through Geysers or Hot Springs.

How is geothermal energy obtained

Humans have developed the ability to interfere with this process by developing technology to harness the power and heat from the water.

Geothermal energy is obtained by drilling into heated rocks close to the surface. Hot water and steam are pumped up through pipes from underground.

In Iceland they drill up to 3000 metres into the rocks for geothermal fluid. This is hot water heated to temperatures of up to 350 degrees Celsius.

Cool water is also pumped down into the heated rocks in the crust and brought back to the surface as hot water.

In Iceland they separate the stream from the hot water. The steam from the heated water is used to turn turbines to generate electricity. For example, at Helisheldi power station.

The hot liquid at 83 degrees is piped to Reykjavik where it is pumped directly to homes and industries and provides hot water for 87% of all homes. It is also piped under the footpaths and roads and this helps keep them ice free during the winter.

Economic benefits of geothermal energy

It can be a source of domestic heating. In Iceland 85% of all homes used geothermal energy as a neat source.

When superheated water reaches the surface it decompresses and turns to steam which drive the turbines to generate electricity. It can be used as a source of cheap and reliable electricity.

It is a cheap source of power and industries are attracted to the cheap source of power. It is reliable as it is available year-round. It reduces the need to rely on imported fossil fuels.

It is also a clean source of power as it is renewable and is sustainable. It has extremely low emissions of Carbon Dioxide compared to burning fossil fuels at power plants. This helps reduce the emissions which cause the Greenhouse effect.

There is also no longer a need to import fossil fuels in these countries. In Iceland, the cheap source of power has attracted metal smelting companies to the country

touristry

It can benefit the tourist industry. In countries such as Iceland the natural heating of bathing pools is a popular tourist attraction. For example, The Blue lagoon where a power plant uses mineral rich water from the power station to fill the lake. The temperature of the water is kept at 38 degrees Celsius year-round. In 2018 just 1.8 million tourists visited Iceland.