What Causes Earthquakes? What are Earthquakes? Earthquakes are trembling's or vibrations of the ground. What Causes Earthquakes? Large rocks in the crust become stuck, when they finally move they release energy which causes an earthquake

The First Break The Focus is the first place that the rock breaks below the surface in an earthquake The break releases energy that is spread as waves through the earth. Seismic Waves – the waves made from the energy released from a break in the rocks in the earths surface The shaking you feel is caused from these waves moving through the ground

Epicentre is the point on the surface directly above the focus.

Animation http://news.bbc.co.uk/2/hi/4126809.stm

How do you measure the strength of the Earthquake? Richter scale

Vocabulary Earthquakes Focus Seismic waves Epicentre Richter scale

Volcanoes

A Volcano is an opening in Earth’s crust through which solid and molten rock, ash and gases escape.

Step 1 Extremely high temperature and pressure can cause the lower mantle to melt and become liquid rock, or magma. This magma expands as it melts and moves upward.

Magma – molten, liquid rock inside the earth

Step 2. The magma, melted or liquid rock, is pushed upward through a weak spot in the earths crust

Step 3. The eruption begins. The Magma reaches the earths surfaces, and now becomes lava. The lava flows from the vent down the volcano’s sides, or comes out violently into the air as a cloud of rock fragments and ash

Step 4. The finest ash particles get carried away by the wind, or settle at the bottom of the sides of the volcano.

Sometimes ash mixes with rain making mud Sometimes ash mixes with rain making mud. This can cause mud flows that races down the sides being very dangerous.

Step 5 and 6 Larger rock fragments fall closer to the vent, smaller ones fall farther away The lava and rock fragments move down the hill because of gravity

Step 7 The magma activity inside the volcano changes the shape of the mountain on the outside, and causes small earthquakes around the volcano.

Vocabulary Volcano Magma Lava Seismogram Surveyor’s level

Positive Negative The dramatic scenery created by volcanic eruptions attracts tourists. This brings income to an area. Many lives can be lost as a result of a volcanic eruption. The lava and ash deposited during an eruption breaks down to provide valuable nutrients for the soil. This creates very fertile soil which is good for agriculture If the ash and mud from a volcanic eruption mix with rain water or melting snow, fast moving mudflows are created. These flows are called lahars. The high level of heat and activity inside the Earth, close to a volcano, can provide opportunities for generating geothermal energy. Lava flows and lahars can destroy settlements and clear areas of woodland or agriculture. Human and natural landscapes can be destroyed and changed forever.