Caused by sudden stress release along faults.
Earth tremor = Small shake. Earthquake = Stronger, more damage.
Focus (Hypocentre) = Where an earthquake starts.
Epicentre = Surface point above the focus.
Richter Scale = Measures earthquake energy.
Seismograph: P-waves first, S-waves second, Surface waves last. More distance = waves spread out.
Earthquake Predictions = Seismic activity + historical data.
Tsunamis grow taller as they reach shallow water.
Earthquake fatalities depend on location, population, and infrastructure.
Measuring Earthquakes:
Indonesia > Australia for earthquakes due to subduction zones.
Deepest earthquakes = Subduction zones. Shallow earthquakes cause more damage.
Earthquake waves: Primary (P) waves travel fastest, followed by Secondary (S) waves, which cause most of the damage.
Fault Types
Normal Fault – Hanging wall moves down due to extension.
Reverse (Thrust) Fault – Hanging wall moves up due to compression.
Strike-Slip Fault – Blocks move horizontally due to shear forces.
Plate Boundaries
Divergent Boundary – Plates move apart, causing normal faults and shallow earthquakes.
Convergent Boundary – Plates collide, causing reverse faults and deep, powerful earthquakes.
Transform Boundary – Plates slide past each other, causing strike-slip faults and frequent earthquakes.
Seafloor spreading - hot magma from the earth’s mantle pushing up through the crust at the bottom of the ocean. This pushes the crust on either side outwards, creating a divergent plate boundary.
Subduction Zones – Areas where one tectonic plate moves under another, leading to intense seismic activity and the formation of deep ocean trenches.
Hotspots – Locations where magma from deep within the Earth rises to the surface, often resulting in volcanic activity and earthquakes, independent of tectonic plate boundaries.
Convergent Boundaries – Occur when two tectonic plates collide, resulting in mountain building, earthquakes, and volcanic eruptions as one plate is forced beneath another.
Ring of fire - string of volcanoes and earthquake activity that exist around the edges of the pacific ocean.
Evidence to support continental drift: Shape of the continent, fossil evidence, rock evidence, glacier evidence.
Continental Crust thicker parts of the crust that makes up earths continents
Oceanic Crust: Thinner parts of the crust that sit under the oceans. More dense than continental crust.
Convergent boundaries - two plates moving towards each other - ocean to continent denser, continent to continent, crumpling occurs, ocean to ocean, denser.
Transform boundaries - two plates sliding past each other, creating a fault line.
Mantle closest to the core heats up and rises due to being less dense.
Compression is when a force is applied to a rock and, if done slowly enough will result in folding.
Anticline fold upwards, forming a shape.
Synticlines fold bend downards.
The point at which the earthquake begins is called the focus. The epicentre of an earthquake is directly above the point below the surface where the movement in the crust began.
Tension is a force that pulls rocks apart.
Seismic Waves:
Body waves - radiate outward and travel through the interior of the Earth
Surface waves - tend to travel only along the Earth’s surface
P-waves are primary waves that are compressional and can travel through solids, liquids, and gases. S-waves - are secondary waves that are shear and can only travel through solids, causing the ground to move perpendicular to the wave direction.
Surface Waves:
Love waves transverse waves that move in a side-toside motion, like a snake.
Rayleigh waves Move with a rolling motion like an ocean wave.
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