Volcanoes and Earthquakes

• Volcanoes are landscape features where melted rock erupts onto the Earth's surface.
• Magma is extremely hot liquid or semi-liquid rock within the mantle.
• Lava is magma that has reached the Earth's surface.
• Hotspots are volcanic regions above anomalously hot mantle areas.
• Black smokers are geothermal vents on the seafloor ejecting superheated, mineral-rich water.
• Active volcanoes are currently erupting or have recently erupted.
• Dormant volcanoes have erupted in the last 10,000 years and are likely to erupt again.
• Extinct volcanoes have not erupted in the last 10,000 years and are not expected to erupt again.
• A caldera is a large, cauldron-like hollow formed after a magma chamber empties during a volcanic eruption.
• A seismograph is an instrument used to detect and measure the intensity of an earthquake.
• The Richter scale is a logarithmic scale that measures the energy released during an earthquake.
• Folding occurs when rocks bend into anticlines or synclines.
• An anticline is a fold in a rock with the narrow point facing upwards.
• A syncline is a fold in a rock with the narrow point facing downwards.
• A fault is a break in the crust where one side moves relative to the other.
• Compression is a squeezing force.
• Tension is a stretching force.
• Shearing is a smearing force.
• A reverse fault is a break where the rock above the fault moves up due to compression.
• A normal fault is a break where the rock above the fault moves down due to tension.
• A strike-slip fault is a break where rocks move horizontally due to shearing.

Earthquakes

• Tremors are minor vibrations of the ground that are commonly not felt.
• Earthquakes are sudden and violent shaking of the ground.
• The focus is the underground location of the fault movement causing an earthquake.
• The epicenter is the surface point directly above the earthquake focus.
• Body waves are seismic waves that quickly travel through the Earth's interior.
• Surface waves are seismic waves that travel slower and only along the surface.
• P-waves (primary waves) are compressional body waves and are the fastest.
• S-waves (secondary waves) are transverse body waves, slower than P-waves, and cannot travel through fluids.
• A tsunami is a powerful ocean wave triggered by an undersea earth movement.

Ocean Features

• Abyssal plains are relatively flat underwater deep ocean floors, around 4000 meters deep.
• Ocean ridges are submarine mountains that tower 2000 meters above the abyssal plains.
• Ocean trenches are narrow and deep troughs in the ocean floor, generally greater than 5000 meters deep.
• Sea-floor spreading is the formation of oceanic crust by rising and melting mantle at ocean ridges.
• Plate tectonics describes the movements and interaction of the Earth's crust plates.
• Convection currents are the movement of particles in a liquid or gas due to temperature or density differences.
• A convergent boundary is where two tectonic plates move towards each other.
• Subduction is a convergent plate boundary where one plate moves under another.
• Collision occurs when two continents crumple together to form a mountain range.
• A mountain range is a group of high ground features, commonly from tectonic collision.
• A divergent boundary is where two tectonic plates move apart.
• A constructive plate boundary is where new crust is formed.
• A transform boundary is where two tectonic plates slide past one another.
• A conservative plate boundary is where crust is neither created nor destroyed.

Earth's Structure

• The crust is the hard and thin outer rock layer of the Earth.
• The mantle is the solid but soft middle rock layer of the Earth.
• The core is the hot center of the Earth made of iron and nickel.
• The outer core is the liquid outer layer of the core, about 2300 km thick.
• The inner core is the solid innermost layer under extreme pressure, with an approximate 1200 km radius.