The Trembling Earth

Thanvi Gunti
Mind Map by Thanvi Gunti, updated more than 1 year ago
Thanvi Gunti
Created by Thanvi Gunti almost 5 years ago


Year 10 Science (The Trembling Earth) Mind Map on The Trembling Earth, created by Thanvi Gunti on 09/28/2016.

Resource summary

The Trembling Earth
  1. Structure of the earth
    1. Crust, mantle, Outer Core and Inner Core
      1. Crust: solid layer, consisting of basalt and granite, 30 km thick and depth up to 1000 0c
        1. Mantle: Semi solid layer, consisting of various metals, 2900 km thick,1000- 2500 0c
          1. Outer Core: Liquid layer, consisting of iron, nickle, oxygen and sulfur, 2300 km thick, 3000- 5000 0c
            1. Inner Core: Solid layer, Consisting of iron and nickle, 1200 km thick, 5000- 6000 0c
            2. Asthenosphere: hot semi-liquid in the upper part of the mantle in continuous movements due to convection currents.
              1. Lithosphere: solid rock. in the upper mantle and the crust that can move.
                1. Geological methods to describe the structure of the earth
                  1. Seismic waves: waves of energy caused by the sudden breaking of rock within the earth. They are recorded on Seismographs. Two types: Body wave and surface waves. Body waves travel through the interior. two types of body waves:
                    1. P waves: They are fast and can travel through solid and liquid so they can be detectable at the other side of the earth. They are longitudinal waves.
                      1. S waves: Slower waves and can travel through solid only and not liquid as they are transverse waves. They are not detectable at the other side of the earth, therefore, the earth's interior must contain liquid.
                  2. The continental drift
                    1. Alfred Wegener hypothesised the earth's continents had moved. His evidence was based on the fact that all the continents seemed to fit together like a 'jig-saw'puzzle and these boundaries were the place he found the same type and age of fossils. He also found that the mountain ranges on different continents matched each other.
                      1. The convection currents in the mantle cause the tectonic plates on the surface of the earth to move in different directions.
                        1. Convection currents: movements in a circular motion within the earth's mantle, caused by the heat of the earth's core. They occur in the asthenosphere.
                          1. The molten magma near the base of the mantle heats up more than the magma above, becoming less dense and therefore rising to the top of the mantle. There it cools down again, becoming more dense than the hot magma underneath and sinking to the bottom with the aid of gravity to repeat the process causing convection currents.
                        2. Seafloor spreading: When the convection currents from the mantle move away from each other, they also move the tectonic plates on the earth's surface., creating a mid oceanic ridge, a gap in the plates where the molten magma can rise up fill the gap and when it cools it creates a new layer of oceanic rock. This process repeats as the plates get pushed further apart, so the newest rocks are in the middle with the oldest rocks on the ends.
                          1. Dating of the rocks on the mid oceanic ridge supports the theory of continental drift as the rocks in the middle are newer than the rocks on the edges of a mid- oceanic ridge. This means that the older rocks had to move apart to make room for the newer rocks to form from molten magma. This means that the continents must move apart to form a gap under the ocean.
                        3. Volcanoes and Earthquakes
                          1. The plate boundaries are the place where most volcanoes can be found and earthquakes occur due to the presence of subduction zones.
                            1. Volcanoes: The convection currents in the earth's mantle make the tectonic plates above them move. When the oceanic and continental boundaries collide as they move towards each other, they create a subduction zone where the more dense oceanic crust slides under the less dense continental crust. Due to the friction of rubbing past the continental crust, combined with the heat from the earth's core, the oceanic crust starts to melt to become molten magma and starts to rise due to release of heat, and tries to escape and make its way to the crust. Once the molten magma breaks through the surface of the earth, it gives rise to a volcano. The magma that reaches the surface is known as lava. Over a period of time, the lava cooling off, layer upon layer, hardens to form rock which build up a volcano.
                              1. Subduction: the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate.
                              2. Earthquakes: The convection currents underneath the earth's surface move the tectonic plates towards each other. They come really close together and the rocky plates press against each other, creating friction which opposes the movement of the jagged rocks. This causes a build up of pressure, which releases when it is too much to stop the resistance of the rock. This release of pressure causes the sudden movement of the rock as it breaks and causes an earthquake.
                                1. The Himalayas: The teectonic plates are moved towards each other by the convection currents. When neither of them subduct after collision, the boundaries are crumpled by the collision. This fractures the crust rocks and the force pushes them upwards to form a chain of mountains. This was how the Himalaya mountnain range formed when the Indian plate collided with the Asian plate.
                                2. Impacts of a volcano
                                  1. Impacts of an earthquake
                                  2. Technological developments
                                    1. Seismographs: Seismology is the study of earthquakes and their shock waves. The sudden release of energy caused by the movement of the tectonic plates, sends out shock waves which are detected and recorded by a seismometer. It is an internal mass attached to an immobile frame. The swinging of the mass caused by the movement of the earth helps record the size and frequency of the waves. These recordings can be later studied and conclusions can be formed according to the patterns that form on the wave graphs.
                                      1. Magnetometers: When pressure builds up near a fault line, the heat generated changes the magnetism of the rocks near it. This change in the Earth's Magnetic feild is measured and recorded using a magnetometer which is placed near the fault line for monitoring. Any large metallic objects can affect the readings, so remote areas give more reliable results. They can also be towed behind in boats or aircraft to provide a reading for a larger area. The bigger the signal the bigger the earthquake is.
                                        1. Seismic survey: send sound waves into the earth and use the time taken for the wave to bounce back to calculate the structure and the materials in the layers of the Earth as the waves are reflected differently at the point of chance in the physical properties of the material. 3D seismic surveys use different observation points on a carefully marked grid to precisely locate different materials and form a 3D cube image of the location. These are commonly used to find minerals in the oceans
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