Physical geography - earthquake,tsunami,volcano

Fault

crack in the earth’s surface where movements have occurred.

Three type of fault

Normal fault, reverse fault, strike-slip fault

Type of fault: Normal fault

When rock is stretched apart or in tension, one side of the fault slips down relative to the other. Hanging wall moves down

Type of fault: Reverse fault

when rock is compressed(pushed) together

Type of fault: Strike-Slip

Two plates slide past each other- go on opposite direction. Usually shallow earthquake

Measuring earthquakes

Measure in Richter Scale (amount of energy released) x3

Earthquake waves

Primary, Secondary,Love wave

Type of wave: Primary (p) Wave

• It is fastest —> first waves to be felt.

• Pushing/pulling, back and forth 

• Travel through solids and liquid 

Type of wave: Secondary (S) waves

• Move slowly and more destructive

• Move up and down or side-to-side

• Only travel through solids 

Type of waves: Surface (Love) Waves 

• One the surface —> most destructive 

• Move like waves in water 

Focus

• Below the surface where the quake occurs

Epicenter

• Above the focus

Liquefaction

The shaking makes water in the soil ries, filling the spaces between paticle. Building and roads sinks

Effects of earthquake (negative)

• Fire 

• Landslides/debris flows/avalanches 

• Dam Failure 

• Tsunamis 

Tsunami

Huge ocean movement caused by sudden movement under water(Earthquake)

Volcano 

Opening in Earth’s crust where magma,gases,ash erupt. Occurs at tectonic plate boundaries and hotspots

Three types of volcano

• Shield

• Composite

• Cinder

Shield 

• Wide, gently sloping with thin and runny lava 

• Low voscosity

• Non-explosive 

• Largest

• Happen in divergent 

Composite

• Steep conical shape with mostly ash and rock

• Built from layer

• Viscous (Sticky)

• Send pyroclastic flows

• Convergent

Cinder cone

• Small steep volcanoes which erupt out of one central vent

• Built from pyroclastic material (ash, lava fragment, and volcanic rock)

• More viscosity

• Short live and explosive

Hot spots

• Unique volcano regions (not a plate boundaries)

• Hot rock rises due to buoyancy creating mantle plume

• Mantle plume —> magma

How does volcanoes formed

• When magma rise to earth surface 

• High pressure to low pressure 

• Principle of density 

• Hot spots 

• Convergent/divergent 

How are volcanoes formed

• Subduction: When oceanic plate sinks, it’s under high pressure and the rock melts. Melted rocks lots of silica rise to mantle. Pressure begins to build in magma chamber.

• Divergent: as plate separates, magma rise upward to fill thje gaps. Colls and solidifies creating new crust

Type of eruption: explosive

• Magma is high viscosity

• High gas and silica content

• ex) composite, cinder

• Mt st Helens

Type of eruption: effusive

• Magma is low viscosity

• Low gas contents

• ex) shield

Lava 

• Molten rocks hat flows on the surface

• forms various structure 

Tephra

• Fragmented volcanic material

• Form pyroclastic flows and ash clouds

Volcanic gases

water vapor, CO2, sulfur dioxide

• Create acid rain and affect climate

Igneous rock

• Form when lava or magma cools and solidifies

lahar 

• Volcanic mudflow carrying debris,water,rock 

• Travels a great distance 

Pyroclastic flow

• Rapidly moving clouds of gas, rock, ash

• Extreamly fast and extreamly dangerous

Ash fall

• Free-falling ash can damage infrastructure

Caldera

Large hallow that forms shortly after the emptying of a magma chamber in a volcanic eruption