Presentation on theme: "Plate Tectonics. The Earth's surface is made up of a series of large plates (like pieces of a giant jigsaw puzzle). These plates are in constant motion."— Presentation transcript:
The Earth's surface is made up of a series of large plates (like pieces of a giant jigsaw puzzle). These plates are in constant motion travelling at a few centimetres per year. The ocean floors are continually moving, spreading from the centre and sinking at the edges. Convection currents beneath the plates move the plates in different directions. Convection currents The source of heat driving the convection currents is radioactive decay which is happening deep in the Earth. Plate tectonics: The main features are:
Converging plate movement When two plates move towards each other, they would collide. Some crust is destroyed due to the impact, therefore this convergent boundary is also called a destructive boundary. When A Continental And Oceanic Plate Collide: Because ocean plates are denser than continental plates, when these two types of plates converge, the ocean plates are subducted beneath the continental plates. Subduction zones and trenches are convergent margins. The collision of plates is often accompanied by earthquakes and volcanoes. When Two Continental Plates Converge : One plate will be forced only slightly under the other, but no subduction will take place. Thus, the pressing together of two plates will fold the crust and forms what we known as fold mountains. When Two Oceanic Plates Converge Subduction may occur or magma will rise up to form volcanoes.
Divergent Plate Movement A divergent plate movement occurs when two plates move away from each other. Divergent takes place at the boundary of the oceanic plates and forms new sea floor. This process is called sea-floor spreading. As magma rises up to the surface, it piles up and solidifies, slowly forming a long chain of mountains on the ocean floor, called an oceanic ridge. Volcanoes can also form undersea at these divergent boundaries, they are called submarine volcanoes and have gentle eruptions.
Transform Plate Movement: is where two plates slide laterally past each other. However, movement is not smooth due to friction between the rocks of the two plates. Therefore, sometimes the two plates would get 'stuck' and lock together. The convection currents of the underlying magma are still dragging the plates, much tension and pressure is built up at the transform boundary. When there is sufficient buildup of pressure, rocks in the plates break and get jerked apart. This results in earthquakes.