EARTHQUAKES Key Vocabulary Stress Focus Compression Epicenter Tension

EARTHQUAKES Key Vocabulary: -Stress -Focus -Compression -Epicenter -Tension -Seismometer -Shearing -P Waves -Surface Waves ##

Continental crust constantly changes over time due to plate tectonics. Forces at plate boundaries are strong enough to break rocks or change their shape.

Stress Force that acts on rock to change its shape or volume Three different kinds of stress can occur in the crust: • Tension • Compression • Shearing

Tension Pulls on the crust, stretching rock so it becomes thinner in the middle Landforms Created by Tension • Mid-ocean ridges – tension causes oceanic crust to spread allowing hot rock from mantle to rise creating high ridges • Continental rifts – when divergent boundaries occur within a continent, they cause enormous splits in the crust

Compression Squeezes rock until it folds or breaks Landforms Created by Compression • Mountain ranges – collision between two continental plates • Ocean trenches – one plate goes under another during collision forming a deep trench where the two plates meet

Shearing Pushes a mass of rock in two opposite directions Landforms Created by Shearing • Transform faults – when plates slide horizontally past each other they form a fault, or a break in the rock of the crust • Fault zones – an area of many fractured pieces of crust along a large fault

Earthquake Vibrations in the ground that result from movement along faults, or breaks in Earth’s lithosphere

Seismic Waves that carry energy of an earthquake away from the focus – point beneath Earth’s surface where rock under stress breaks to cause an earthquake epicenter, or point on the surface directly above the focus

Three types of Seismic Waves • Primary waves (P waves) – compression waves that travel through solids and liquids, compressing and expanding the material they pass through, temporarily changing volume • Secondary waves (S waves) – only travel through solids and temporarily change the shape, but not the volume of the material they pass through; move slower than P waves • Surface waves – move slower than P and S waves, but can produce severe ground movement with a wavelike motion

1 = most damaging 4 = least The closer the earthquake is to the surface of the earth, the stronger it will be deep What types of earthquakes cause the most damage? 4 3 Low magnitude High magnitude 2 1 shallow

How are earthquakes described? Intensity: measures the amount of shaking at a location based on damage Magnitude: measures the size of waves/the amount of energy released in an earthquake Magnitude is more important

Locating an Earthquake’s Epicenter Done using triangulating data from at least three different seismometers, or devices that measure and record ground motion and helps determine the distance seismic waves travel.

How long does it take for a p-wave to travel 2000 km? How long does it take an s-wave to travel 2000 km? How far does an s-wave travel in 10 min? How far does a p-wave travel in 10 min? What happens to the time difference between primary and secondary waves as the distance traveled gets longer? Suppose a p-wave and a s-wave start together and travel for 5 minutes. Which will travel farther?

Final Exam Scientists are studying a graph showing the time differences between the seismic P-waves and the seismic S-waves as they travel through Earth. Which information can they learn from the graph? A. the magnitude of an earthquake B. the duration of an earthquake C. the epicenter of an earthquake D. the intensity of an earthquake

Final Exam Scientists are studying a graph showing the time differences between the seismic P-waves and the seismic S-waves as they travel through Earth. Which information can they learn from the graph? A. the magnitude of an earthquake B. the duration of an earthquake C. the epicenter of an earthquake D. the intensity of an earthquake

VOLCANOES • • • Key Vocabulary: -Volcano -Magma -Lava -Pyroclastic Flow -Lahar

Volcano Weak spot in earth’s crust where molten material, or magma, comes to the surface magma – molten mixture of rock-forming substances, gases and water from the mantle; when magma reaches Earth’s surface it is called lava

At plate boundaries the crust often fractures due to the diverging (pulling) or converging (pushing) plates. As a result, these fractures allow magma to reach the surface forming volcanic belts along the boundaries of Earth’s plates.

Ring of Fire Major belt is the Ring of Fire, formed by many volcanoes that rim the Pacific Ocean.

Inside a volcano is a system of passageways through which magma move. This system includes a magma chamber, pipe, vent, lava flows and a crater vent magma chamber pipe

Geologists classify volcanic eruptions as quiet or explosive: Lahar– magma has low silica content, flows easily and erupts quietly with gases bubbling out gently and lava oozing quietly (VIDEO) 2

pyroclastic flow– has magma high in silica with trapped gases building up pressure until they explode with incredible force Mt. Otake (Sept. 2014) A pickup truck flees from the pyroclastic flows spewing from the Mt. Pinatubo volcano in the Philippines, on June 17, 1991. This was the second largest eruption of the 21 st century.

dormant volcano – not active, but may become active extinct volcano – unlikely to erupt again

Landforms from Lava and Ash

Geothermal Activity Occurs when magma, a few kilometers, beneath Earth’s surface heats underground water Hot Springs formed when groundwater is heated by a nearby body of magma or hot rock and eventually rises to the surface to collect in a natural pool.

Geyser Fountain of water and steam that erupts from the ground when buildup of pressure is released.

Videos about volcanoes • Violent volcanoes • Papua New Guinea Volcano Eruption