Earthquake Risk:
Why is Queen Charlotte at risk of a natural disaster?
What is an earthquake?
An earthquake can be defined as a sudden movement of the ground, occuring most oftn along a fault (which is a crack in the Earth's crust), that realeases energy in the form of waves.
How does the Earth's inner geography contribute to the formation of this phenomenon?
In the Earth's core, there is very high pressure, however, in sharp contrast to the core, when you rise to the Earth's crust, the pressure and heat in lost. When molten lava (heated rock) is put under considerable thermal and physical pressure deep into the Earth, it rises up to the Earth's crust beacuse it loses its density. Having reached the colder crust, it promptly cools down and makes it way down again. This perpetual heating and cooling causes pressure on the tectonic plates that lie in the Earth's crust, leading them to release the pressure in the form of movement.
Tectonic Plates and Their Consequences
The aforementioned plates that lie in the Earth's crust release the built up energy from the convection currents in the form of movement that triggers the collision, separation or parallel movement of the plates. These three types of movement entail a release in energy in the form of waves. Incidentally, there are three types of waves as well that occur one after the other for varying amounts of time. The first wave, named the primary wave, shakes the Earth horizontally, the secondary wave shakes vertically and the third wave, the surface wave, strikes the surface of the Earth in a zig-zag pattern. These waves and shaking can entail substantial damage to a landscape, particularly to buildings and infrastructure.
Types of Plate Boundaries and Their Effects on a Landscape
The convection currents mentioned above cause the movement of the tectonic plates that lie in the Earth's crust. There are three types of tectonic plates that show particular characteristics at their boundaries.
For one, there are the convergent plate boundaries. This plate boundary consists of the collision of two plates, which then gradually become larger. Depending on the types of boundaries that are colliding, being either continental oceanic, this movement can produce very different effects.
The collision of two continental plates would entail the formation of a mountain chain, because both plates have the same density (both being continental, and therefore equally light) and so they both push up to form the topological feature. The convergence of one continental and one ocean plate would bring forth subduction, as the denser plate (the oceanic plate) sinks underneath the continental one and pushes to produce a fault (a crack in the Earth's crust) that causes vulnerability when it comes to earthquakes. The convergence of two oceanic plates brings forth the formation of a trench because both plates have the same density and push underneath one another. The convergent plate boundary produces earthquakes and tsunamis in addition to the mountain ranges and faults, thus making it the most destructive of the plate boundaries.
The second type of plate boundary is the divergent plate boundary. This consists of two plates moving away from one another, and therefore becoming larger in the process. This type of plate boundary most often produces volcanoes and occurs along a mid-ocean ridge, although it can also take place on land.
The final type of plate boundary is the transform plate boundary. This embodies the parallel movement of two plates. This sliding movement can occur withot the occurence of any earthquakes, however, if two plates lock up on one another for a long periodof time, when they detach, this produces a release in energy that can demand for a very substantial and destructive earthquake.
Skvir, Jonathan. "Transform Plate Boundaries." Delran Middle School- Plate Tectonics Chapter Three. N.p., n.d. Web. 4 Feb. 2016.
The focus is the point of movemnt along a fault. But notice the waves!
"Seismic Waves Radiate from the Focus of an Earthquake." Science Learning. University of Waikato, 21 July 2007. Web. 4 Feb. 2016. <http://sciencelearn.org.nz/Contexts/Earthquakes/Sci-Media/Images/Seismic-waves>.
"Convection Currents." Introduction to the Theory of Plate Tectonics. Wikispaces, n.d. Web. 4 Feb. 2016. <http://saulscience.wikispaces.com/Geology>.
Skvir, Jonathan. "Convergent Plate Boundaries." Delran Middle School- Plate Tectonics Chapter Three. N.p., n.d. Web. 4 Feb. 2016.
Skvir, Jonathan. "Divergent Plate Boundaries." Delran Middle School- Plate Tectonics Chapter Three. N.p., n.d. Web. 4 Feb. 2016.
