1 2 Sudden Earth Events earthquakes or volcanoes

1. 2 Sudden Earth Events (earthquakes or volcanoes)

Earthquakes 1. 2. 3. 4. Trembling or vibrations of the ground, caused by the sudden release of energy that has slowly been building up in Earth’s crust. Large masses of rock in the crust move and sometimes become locked together or stuck. A tremendous force is created until finally the rocks break. This sudden break causes an earthquake.

There are 3 types of seismic waves that occur in an earthquake. n 1) Primary (P-waves) – these are the fastest of the 3 waves and arrive first on Earth’s surface to warn people in earthquake areas. n

2) Secondary (S-waves) – travel more slowly than P-waves and can pass only through solids, not liquids or gases. n 3) Surface Waves – are the slowest, but their rolling motion breaks up roads and buildings, so they do the most damage. n

Focus – first place that the rock breaks below the surface in an earthquake n Seismic Waves – shock waves caused by an earthquake. n Epicentre – point on the surface directly above the focus n

When P & S-waves reach the epicenter they generate the surface waves which travel outward like water ripples from a stone being tossed into water. n Example n

Water displaced by an earthquake is called a tsunamis (huge waves). n Liquefaction is the process of changing into a liquid-like substance such as quicksand. The sandy base is turned into quicksand, and many buildings fall over. n

n Richter Scale – scale developed by Charles Richter that measures the magnitude of an earthquake. Scale starts at 0, and each increase of 1 means an increase of 10 times the amount of ground motion.

n n n Generally earthquakes of 2 or less are not felt. Magnitudes of 5. 0 -5. 9 create damaging shocks. 6. 0 -6. 9 are destructive in populated regions. Approximately 18 earthquakes per year are considered major: 7. 0 – 7. 9. Magnitudes higher than 8. 0 produce total destruction to communities.

Volcano – an opening in Earth’s crust through which solid and molten rock, ash, and gases escape. n Pg 360 – diagram of a volcano n

When volcanoes are not active they are described as dormant. n Ring of fire is an area of volcanoes around the Pacific ocean n

Lava – molten rock that flows out of a volcano. n Ash – fine, burnt particles from a volcanic eruption. n Magma – molten rock inside Earth. n

Seismograph – device that detects the waves of energy that spread through the earth from the focus of an earthquake. n Surveyor’s Level – device that measure minute changes in the angle of the ground’s slope. n Seismogram – print out of seismograph n

n The earliest seismograph was invented in China A. D. 136 by a man named Choko.

Historic Canadian Earthquakes

Volcanoes n Oh My God n seismic seconds n