Running head: EARTHQUAKES
Earthquakes are rapid movements of the earth's crust along a fault line. They are usually
accompanied by sound. Sometimes earthquakes have foreshocks that are smaller earthquakes
which are followed by larger earthquakes. However, this is not practical always and scientists do
fail short of knowledge on whether an earthquake is a foreshock until the shocking earthquake
occurs. Aftershocks come after large earthquakes and last for weeks, months or even years.
Unlike an earthquake; an earth tremor is a less violent shaking of the earth's crust. However, both
an earthquake and a tremor indicate that earth is not completely stable ("BBC Bitesize Earthquakes - OCR - Revision 1," n.d.).
The Cause of Earthquakes
Earthquakes are brought by sudden shifts of huge rock masses in the earth's crust which
is the top layer of the earth. The rocks are called tectonic plates and they are usually in constant
motion. Their edges are called tectonic boundaries made of faults along which earthquakes
occur. Earthquakes happen along fault lines, fractures or volcanic eruptions where magma or
subterranean volcanic materials that displace rocks in the crust of the earth ("Chapter 11
Earthquakes – Physical Geology," n.d.).
The disruption of rocks results in waves or vibrations which are sent to the earth’s surface
as shocks. The focus or origin is the point where disturbance occurs and is usually in the upper
20 km of the earth’s crust. The earthquake is most felt in the epicenter which is a point on the
surface of the earth and positioned above the focus ("Chapter 11 Earthquakes – Physical
Geology," n.d.). Seismic waves or shocks are the waves sent out by an earthquake. When they
occur in oceans earthquakes create ocean waves known as tsunamis which are usually very
Earthquakes can be triggered by natural causes such as tectonic movement, gravitational
pressure, and volcanic activity and isotactic adjustment. Tectonic movement happens when large
rigid blocks of the earth’s crust called plates cause stress to build up at their edges. The rocks
thus fracture at their boundaries releasing sudden energy causing seismic vibrations whose effect
is felt as earthquakes. In Japan, this is the major cause of earthquakes. Gravitational pressure
causes an earthquake when magma eruption leaves hollows in the earth's interior where the
chambers collapse due to gravity and cause the earth to shake ("BBC Bitesize - Earthquakes OCR - Revision 1," n.d.).
Volcanic activity is the process through which hot molten rock in the interior of the earth
known as magma rises into the earth's crust or surface. Sudden magma movement, volcanic
explosions and violent emissions of volcanic gases shatter rocks releasing energy in form of
seismic waves. Isotactic adjustment is balancing of the earth's crust that occurs when pressures
change. The adjustment causes rock movement breaking rocks and causing an earthquake
("Chapter 11 Earthquakes – Physical Geology," n.d.). Canada is a temperate region covered by
large glaciers, when the glaciers melt in large scale such adjustment has to occur due to loss of
Shock waves that cause earthquakes can also be trigger...