Plate tectonics; what are they?
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The theory of plate tectonics provides geology with a comprehensive theory that explains ‘how the earth works’. The formula was formulated in the 1960s and 70s as new information was obtained about the nature of the ocean floor- earth’s ancient magnetism, the distribution of volcanoes and earthquakes, the flow of heat from Earth’s interior and the worldwide distribution of plant and animal fossils. Plate tectonics states that the earth’s outermost layer, the lithosphere is broken into 7 large, rigid pieces called plates: the African, North American, Eurasian, Australian, Antarctic and Pacific Plates. Several minor plates also exist known as the Arabian, Nazca and Philippines plates.The plates are all moving in different directions and at different speeds (at around the speed f your fingernails grow) in relationship to each-other.The plates move like cars in a demolition derby, which means they sometimes crash into each-other, pull apart or sideswipe each-other. The place where the two plates
meet is called a plate boundary. Boundaries have different names depending on how the two plates are moving in relationship to each-other.
meet is called a plate boundary. Boundaries have different names depending on how the two plates are moving in relationship to each-other.
What are faults?
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Plate tectonics are constantly moving, whether it is by a few centimetres per year. Such plates make up the top layer of the earth called the
lithosphere. Directly under that layer is the asthenosphere. It’s a flowing area of molten rock. There is constant heat and radiation given off form the centre of the earth.That energy is what constantly heats the rocks and melts them.The tectonic plates are ‘floating’ on top of the molten rock and moving round the planet.Think of it as ice at the top of your soda. When the continents and plates move it is called continental drift. Think of the molten rock in the asthenosphere, not as rock, but as a liquid. It has currents and it flows just like any other liquid.
When the floating rocks spread apart it is called spreading centre. When the rocks move closer together it is called the subduction zone. When they are forced together it is called a zone of convergence. When this happens, one of the plates usually moves under the other in a zone of convergence. As plates move down lower into the atmosphere they begin to melt. The place where they meet has a crack of a trench. Some of the deepest parts of the oceans are such trenches.
lithosphere. Directly under that layer is the asthenosphere. It’s a flowing area of molten rock. There is constant heat and radiation given off form the centre of the earth.That energy is what constantly heats the rocks and melts them.The tectonic plates are ‘floating’ on top of the molten rock and moving round the planet.Think of it as ice at the top of your soda. When the continents and plates move it is called continental drift. Think of the molten rock in the asthenosphere, not as rock, but as a liquid. It has currents and it flows just like any other liquid.
When the floating rocks spread apart it is called spreading centre. When the rocks move closer together it is called the subduction zone. When they are forced together it is called a zone of convergence. When this happens, one of the plates usually moves under the other in a zone of convergence. As plates move down lower into the atmosphere they begin to melt. The place where they meet has a crack of a trench. Some of the deepest parts of the oceans are such trenches.
ever wonder if the theory of plate tectonics is actually true???
Many wonder if such ideas area actually true! How do scientists back up such ideas when they cannot see or reach the centre to prove it? Scientists have travelled all over the
earth and found evidence that supports the ideas of plate tectonics. First, they looked at all the continents. Ever notice how Africa and South America
look like they could fit together? Scientists did that exact thing. They cut up a map, moved the continents closer together, and came up with a huge landmass known as Pangaea (one super-continent). Scientists also looked at the fossils on different continents. They found that fossils on Australia were similar to the ones in Southern Asia. They think the same plants once lived on continents, but when they split apart, new plants developed. Specific types of rocks also prove the theory of plate tectonics. The west coast of Africa has very similar rock formations to those on the East Coast of South America. They are too similar to be a coincidence.
earth and found evidence that supports the ideas of plate tectonics. First, they looked at all the continents. Ever notice how Africa and South America
look like they could fit together? Scientists did that exact thing. They cut up a map, moved the continents closer together, and came up with a huge landmass known as Pangaea (one super-continent). Scientists also looked at the fossils on different continents. They found that fossils on Australia were similar to the ones in Southern Asia. They think the same plants once lived on continents, but when they split apart, new plants developed. Specific types of rocks also prove the theory of plate tectonics. The west coast of Africa has very similar rock formations to those on the East Coast of South America. They are too similar to be a coincidence.
what relationship do plate tectonics share with earthquakes, tsunamis and volcanoes?
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The World’s earthquakes and volcanoes are not randomly distributed over the Earth’s surface. Earthquakes are caused by movements of
plates underneath e Earth’s surface. The places where these plates meet are breaks in the Earth’s crust called faults. Earthquakes happen when plates move along the faults in different directions. These shifting plates create energy that is called seismic waves. These waves move outward waves travel underneath the Earth’s surface, through solids, liquids and gases. When energy is released form such disturbances intense waves travel at a fast pace causing vibrations and shake the ground. When this happens, just like waves that are formed by a
disturbance in a body of water (picture the rings that form in a lake when you throw a pebble) seismic waves travel at a fast pace releasing energy. Volcanic earthquakes are also quite common, molten rock, called magma, is stored in reservoirs under volcanoes. As this magma moves upwards, it can fracture the rock it squeezes through, causing earthquakes, usually with magnitudes much
greater than 5.00 on the Richter scale. Sometimes the magma collects in a high level reservoir previous to a volcanic eruption as it moves around and causes
bursts of continuous vibrations. Body volcanoes nearby can awaken, from the force and power of the waves, as well as the energy release. This causes an
eruption.Tsunamis are also caused from the force and energy created by earthquakes- when an earthquake takes place, especially under the ocean’s surface, energy is released in the form of seismic waves, the water in the ocean is displaced and has nowhere to go, except dry areas which are inhabited by millions of people!
plates underneath e Earth’s surface. The places where these plates meet are breaks in the Earth’s crust called faults. Earthquakes happen when plates move along the faults in different directions. These shifting plates create energy that is called seismic waves. These waves move outward waves travel underneath the Earth’s surface, through solids, liquids and gases. When energy is released form such disturbances intense waves travel at a fast pace causing vibrations and shake the ground. When this happens, just like waves that are formed by a
disturbance in a body of water (picture the rings that form in a lake when you throw a pebble) seismic waves travel at a fast pace releasing energy. Volcanic earthquakes are also quite common, molten rock, called magma, is stored in reservoirs under volcanoes. As this magma moves upwards, it can fracture the rock it squeezes through, causing earthquakes, usually with magnitudes much
greater than 5.00 on the Richter scale. Sometimes the magma collects in a high level reservoir previous to a volcanic eruption as it moves around and causes
bursts of continuous vibrations. Body volcanoes nearby can awaken, from the force and power of the waves, as well as the energy release. This causes an
eruption.Tsunamis are also caused from the force and energy created by earthquakes- when an earthquake takes place, especially under the ocean’s surface, energy is released in the form of seismic waves, the water in the ocean is displaced and has nowhere to go, except dry areas which are inhabited by millions of people!
what is the richter scale? what do the numbers represent?
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The Richter scale, officially called the ‘Richter Magnitude Scale,’ was developed in 1935 and is a numerical value used to measure the
power of earthquakes. It is a scale used to measure the amplitude of waves recorded by a seismograph. Earthquakes measured on at less than about 2.0 on the Richter scale are not very serious, and can barely be measured let alone felt. An earthquake is usually considered much more serious, and felt by most people if measure around 5.0 and higher.
An earthquake measuring 6.0 on the Richter scale has a magnitude ten times greater than that of a 5.0 quake. One whole number increase also
indicates that about 31 times more energy was released during a quake. It is theoretically impossible for there to be an earthquake of 10.0 or stronger, as such has never been recorded. Such a quake would be classified as massive, and cause devastation across a very widespread area. Keep in mind though that the type of earthquake hitting an area and the damage it will cause greatly depends
on where. For example, a 5.0 magnitude earthquake hitting a densely populated area with old or poorly constructed buildings would do more damage that a 7.0 magnitude earthquake that occurs in a remote region with very few people and structures.
Earthquakes are measured using seismographs which record the magnitude of an earthquake. These devices detect waves traveling through the earth in a series of lines that move up and down. Greater movement in the earth creates more of a difference in the amplitude.
By Tijana Chetcuti - 9B ©
power of earthquakes. It is a scale used to measure the amplitude of waves recorded by a seismograph. Earthquakes measured on at less than about 2.0 on the Richter scale are not very serious, and can barely be measured let alone felt. An earthquake is usually considered much more serious, and felt by most people if measure around 5.0 and higher.
An earthquake measuring 6.0 on the Richter scale has a magnitude ten times greater than that of a 5.0 quake. One whole number increase also
indicates that about 31 times more energy was released during a quake. It is theoretically impossible for there to be an earthquake of 10.0 or stronger, as such has never been recorded. Such a quake would be classified as massive, and cause devastation across a very widespread area. Keep in mind though that the type of earthquake hitting an area and the damage it will cause greatly depends
on where. For example, a 5.0 magnitude earthquake hitting a densely populated area with old or poorly constructed buildings would do more damage that a 7.0 magnitude earthquake that occurs in a remote region with very few people and structures.
Earthquakes are measured using seismographs which record the magnitude of an earthquake. These devices detect waves traveling through the earth in a series of lines that move up and down. Greater movement in the earth creates more of a difference in the amplitude.
By Tijana Chetcuti - 9B ©
richter scale chart:
Magnitude:
- 2.0 or less - 2.1 - 3.9 - 4.0 - 4.9 - 5.0 - 5.9 - 6.0 - 6.9 - 7.0 - 7.9 - 8.0 - 9.9 |
Class:
- Micro - Minor - Light - Moderate - Strong - Major - Great |
Effects:
- Cannot be felt. - Many are not usually felt and cause minor damage. - Can be felt, although causes minor damage. - Can cause slight to moderate damage to buildings. - Can cause significant damage, especially to populated areas - Causes serious, widespread damage. - Extremely destructive! Can completely destroy entire communities. |