Earthquakes at Transform Plate Boundaries ( Read ) | Earth Science | CK Foundation
The Earth is formed of several layers that have very different physical and Most earthquakes occur at the boundaries where the plates meet. In fact Spreading zones usually have earthquakes at shallow depths (within Subduction zones occur when one or both of the tectonic plates are Where continental crust meets continental crust The most active divergent plate boundaries are between oceanic plates and are often called mid-oceanic ridges. 3. Earthquakes happen when rock below the Earth's surface move. Causing the Earth's surface to crack the closer you are to the plate boundaries.
Tectonic Plates and Plate Boundaries
There are major plates and many minor plates. Varying between 0 to mm per year, the movement of a plate is driven by convection in the underlying hot and viscous mantle.
Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries in zones that may be anything from a few kilometres to a few hundred kilometres wide. To watch a simulated fly-by along New Zealand's plate boundary check out this video.
- 4. Earthquakes Occur Along Fault Lines -
- 5. Earthquakes Occur Along Plate Edges -
There are three main types of plate boundaries: Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust. The denser plate is subducted underneath the less dense plate.Bill Nye Plate Tectonics, Volcanoes and Earthquakes
The plate being forced under is eventually melted and destroyed. Where oceanic crust meets ocean crust Island arcs and oceanic trenches occur when both of the plates are made of oceanic crust. Zones of active seafloor spreading can also occur behind the island arc, known as back-arc basins.
These are often associated with submarine volcanoes. Where oceanic crust meets continental crust The denser oceanic plate is subducted, often forming a mountain range on the continent.
They are more common near the edges of the plates.
Types of Faults Normal faults are the cracks where one block of rock is sliding downward and away from another block of rock. These faults usually occur in areas where a plate is very slowly splitting apart or where two plates are pulling away from each other.
A normal fault is defined by the hanging wall moving down relative to the footwall, which is moving up. Figure 2 - A normal fault.
Earthquakes | How Plates Move | Where Earthquakes Occur and How They are Measured
The 'footwall' is on the 'upthrown' side of the fault, moving upwards. The 'hanging wall' is on the 'downthrown' side of the fault, moving downwards. Reverse faults are cracks formed where one plate is pushing into another plate. They also occur where a plate is folding up because it's being compressed by another plate pushing against it. At these faults, one block of rock is sliding underneath another block or one block is being pushed up over the other.
A reverse fault is defined by the hanging wall moving up relative to the footwall, which is moving down.
BBC - GCSE Bitesize: Volcanoes and earthquakes
Figure 3 - A reverse fault. This time, the 'footwall' is on the 'downthrown' side of the fault, moving downwards, and the 'hanging wall' is on the 'upthrown' side of the fault, moving upwards.
When the hanging wall is on the upthrown side, it 'hangs' over the footwall.
Strike-slip faults are the cracks between two plates that are sliding past each other. You can find these kinds of faults in California. The San Andreas fault is a strike-slip fault.