# BOUNDARIES Convergent Divergent Transform Why do we need

• Slides: 16

BOUNDARIES • Convergent • Divergent • Transform • Why do we need to know all three and how they work? What is the importance?

PLATE TECTONIC MOVEMENTS • Movement of the North American Plate is about 2. 5 cm Per Year. • The Earth 250 million years ago had all of the continents together except Australia. • About 100 Million years ago most of the continents were separated. • What is causing the movement? • Link (1: 09): Candle and a Pinwheel • Link (0: 20): Candle Powered Pinwheel

LAYERS OF THE EARTH • Layers of the Earth • Oceanic Plate vs Continental Plate • The main difference is that Oceanic plate is thinner and more dense while continental plates are less dense and usually have the oceanic plate subducting underneath them. • The Mantle is the largest layer and very hot to the point that it melts down the plates from subduction and turns them back into molten rock. • The consistency of the Mantle is like playdough or a melted starburst.

WHAT COMES NEXT? ? • Divergent: • Sea floor spreading • Rift valleys • Convergent: • Collide • Subduction • Volcanoes and Mountains • Transform: • Continental Crust • Earthquakes Find an example of each boundary in the united states. Find an example of each that caused a catastrophic event.

• Seismic Waves are waves of energy caused by the sudden breaking of rock within the Earth. Can also be generated by explosions or impacts. • https: //www. youtub e. com/watch? v=e 7 ho 6 z 32 yyo

• Seismic Waves "body waves", called body waves because they propagate (move) through the “body” of the Earth. • A seismic wave that travels across the surface of the Earth as opposed to through it. Surface waves usually have larger amplitudes and longer wavelengths than body waves, and they travel more slowly than body waves do.

• are compression waves • fastest kind of seismic wave • move through solid and liquid rock • pushes/pulls as it moves through PRIMARY WAVES This type of wave cracks and fractures the crust. The back and forth motion is like a slinky being pushed and pulled. https: //www. youtube. com/watch? v=gl 4 Fv HKz. Al. U

• are transverse waves • only move through solid rock • slower than P-Waves • up/down or side to side motion • second wave felt during earthquakes (after PWaves) SECONDARY WAVES

SURFACE WAVES • The most violent wave that results in catastrophic results. • Although they're slower than either P-waves or S-waves, they have large amplitudes, and that full amplitude is focused on the surface of the earth. This is why they cause more damage. Love waves are the most dangerous of all kinds of seismic waves. They are faster than Rayleigh waves and even larger in amplitude.

• What is a seismograph? • an instrument that measures and records seismic waves • generally used for detecting and measuring earthquakes • also detects/measures volcanic events and explosions • Link (1: 04): How a Seismograph Works SEISMOGRAPHS

SEISMOGRAM • a seismogram is the graph output from a seismograph. • Richter Scale: a 1 to 9 scale for measuring seismic waves • Each level is ten times greater than the previous level. Seismogram from Alaska

Draw a model of Earth’s structure from the data. Crust Depth: 0 to 50 km Outer Core Depth: 2900 to 5200 km Mantle Depth: 50 to 2900 km Inner Core Depth: 5200 to 6400 km

EARTH’S INTERNAL STRUCTURE • Seismic waves change speed and refract (bend) as they move through different rock layers. SWaves stop at liquids. • Understanding this enabled us to analyze seismographic data which reveals Earth’s internal structure.