Earth’s Interior: Heat, Tectonic Plates, Earthquakes, and Volcanoes
1. Why is the Earth’s Interior so Hot?
The Earth’s interior is hotter than the exterior because of the heat generated when the Earth was formed. The temperature in the inner core is hotter (above 6,000ºC) than the surface of the Sun. The temperature increases by about 25ºC for every kilometer in depth.
4,600 Million Years Ago
Giant meteorites continually collided with the Earth. The heat they contained made the Earth hotter.
4,000 Million Years Ago
As the Earth heated up, it expanded. Metal material sunk to the center of the Earth. These formed a nucleus made up mainly of iron.
The Earth Today
The Earth today has two cores. The inner core is solid, due to the tremendously high pressure at the center of the Earth. The outer core, however, is molten.
2. What are Tectonic Plates?
The intense heat from the inner core of the Earth causes material to move in the liquid outer core and the mantle. This movement may produce tectonic plates, made up of the crust and the upper mantle. Tectonic plates are massive slabs of solid rock. The large plates move extremely slowly over the surface of the Earth.
Distribution of Tectonic Plates
Earthquakes, volcanic eruptions, mountain-building, and other phenomena occur along tectonic plate boundaries. Geysers are further evidence of the heat that comes from the interior of the Earth. A geyser is a natural eruption of water, steam, and other gases which rise up through cracks in the surface of the Earth.
3. What Phenomena Does Internal Energy Produce?
Earthquakes and volcanoes are examples of phenomena caused by the internal energy produced by the heat inside the Earth.
Volcanic Eruptions
A volcano is a place on the surface of the Earth where molten rock and gases are ejected through the crust. Volcanoes vary in their structure. Some are cracks in the crust where lava erupts. Others are domes, shields, or mountain-like structures with a crater at the summit. During a volcanic eruption, materials in solid, liquid, and gaseous form are expelled from the interior of the Earth. Molten rock below the Earth is lighter than the solid matter above it. When the molten rock finds a fracture in the surface of the Earth, it erupts and the gases escape. The molten rock spills out to form rivers of lava.
At the base of the crust and the upper layer of the mantle, there is a mixture of molten rock and gases which is known as magma. During a volcanic eruption, magma is expelled to the exterior through a volcano, which is an opening in the Earth’s crust. When magma erupts, it releases its gases and turns into lava. Liquid lava can be viscous and slow-moving or thin and fluid. The higher the temperature, the more fluid the lava. During a volcanic eruption, the most abundant gases released are carbon dioxide and water vapor. Carbon dioxide and sulfur are also released.
4. How are Earthquakes Produced?
An earthquake is a violent shaking of the Earth’s crust which lasts a short time and varies in intensity. It is caused by a sudden release of energy in the crust. This energy travels in seismic waves. Energy released during earthquakes and volcanic eruptions can also cause a tsunami, or huge wave. Tsunamis can flood areas near the coast and cause terrible material damage and the loss of many lives. An earthquake is measured on the Richter Scale. This scale, numbered from 1-10, reflects the amount of energy released at the hypocenter of an earthquake. The biggest earthquake ever recorded was registered in Chile in 1960. It measured 9.5 on the Richter Scale. The waves which travel through the Earth are called seismic waves. They travel spherically outwards from the origin of the earthquake, which is known as the hypocenter. The epicenter is the point on the Earth’s surface which is directly above the hypocenter. From the epicenter, seismic waves travel through the surface as superficial waves.
Steps to Reduce Damage by Earthquakes and Volcanoes
The following steps can help you reduce damage from earthquakes and volcanoes:
Prediction
This means studying the possibility of damage by earthquakes and volcanoes. It includes risk maps which show the probability of earthquakes and volcanic eruptions.
Preparedness
This refers to the safety measures adopted to minimize damages in case of a disaster. For example, in areas of high risk from earthquakes:
- Buildings are designed to withstand seismic movement
- The local population is shown what to do during an earthquake
- Police and fire services are trained to evacuate the population
Protect Our Planet
Waste harms and pollutes the environment. Appropriate waste disposal can reduce environmental damage. You can make a difference if you practice the three Rs.
Reduce
Tips on how to reduce:
- Use your own grocery bag, your own water bottle, etc.
- Don’t buy things with a lot of packaging. Simpler packaging reduces waste.
- Use durable products for as long as possible.
- Repair appliances when they break, instead of throwing them away.
- Buy and use less! Buy only what you need and use all of what you buy.
Recycle
Tips on how to recycle:
- Use the right recycling bins.
- Making new things from recycled ones requires less energy than making things from new materials.
- Don’t throw away anything that can be recycled!
Reuse
Tips on how to reuse:
- Use your own grocery bag, your own water bottle, etc.
- Use cloth serviettes instead of paper ones.
- Repair things when they break, instead of replacing them.
- Donate clothes, blankets, etc., to others who can use them.
- Always remember that one person’s trash is another person’s treasure!