Earth’s crust is divided into two types: oceanic crust and continental crust. The transition zone between these two types of crust is sometimes called the Conrad discontinuity. Silicates (mostly compounds made of silicon and oxygen) are the most abundant rocks and minerals in both oceanic and continental crust.

Divergent boundaries occur along spreading centers where plates are moving apart and new crust is created by magma pushing up from the mantle. Picture two giant conveyor belts, facing each other but slowly moving in opposite directions as they transport newly formed oceanic crust away from the ridge crest.

There are three kinds of plate tectonic boundaries: divergent, convergent, and transform plate boundaries. This image shows the three main types of plate boundaries: divergent, convergent, and transform.

They include mountains, plateaus, and rift valleys. Whereas erosion shapes landforms, their origins lie in tectonic processes that build the major structures of the Earth.

The heat from radioactive processes within the planet’s interior causes the plates to move, sometimes toward and sometimes away from each other. This movement is called plate motion, or tectonic shift.

They move at a rate of one to two inches (three to five centimeters) per year.

In this lesson, we explore the causes of plate movement, including thermal convection, ridge push and slab pull. Students will learn how these processes complement each other and form a theory for tectonic plate movement.

When the plates move they collide or spread apart allowing the very hot molten material called lava to escape from the mantle. When collisions occur they produce mountains, deep underwater valleys called trenches, and volcanoes. The Earth is producing “new” crust where two plates are diverging or spreading apart.

If two tectonic plates collide, they form a convergent plate boundary. Usually, one of the converging plates will move beneath the other, a process known as subduction. The new magma (molten rock) rises and may erupt violently to form volcanoes, often building arcs of islands along the convergent boundary.

Without plate tectonics, Earth would not have its diverse geography, which provides a wide range of habitats. Plate tectonics is also responsible for hydrothermal vents on the ocean floor.

An earthquake is caused by a sudden slip on a fault. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth’s crust and cause the shaking that we feel. In California there are two plates – the Pacific Plate and the North American Plate.

Causes of Earthquakes in General

• Induced Earthquakes. Induced quakes are caused by human activity, like tunnel construction, filling reservoirs and implementing geothermal or fracking projects.
• Volcanic Earthquakes. Volcanic quakes are associated with active volcanism.
• Collapse Earthquakes.

Things that cause earthquakes

• Groundwater extraction – decrease in pore pressure.
• Groundwater – increase in pore pressure.
• Heavy rain.
• Pore fluid flow.
• High CO2 pressure.
• Building dams.
• Earthquakes.
• No earthquakes (Seismic quiescence)

Earthquake is a term used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip, or by volcanic or magmatic activity, or other sudden stress changes in the earth.

Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little. When the rocks break, the earthquake occurs.

There are many different types of earthquakes: tectonic, volcanic, and explosion. The type of earthquake depends on the region where it occurs and the geological make-up of that region. The most common are tectonic earthquakes.

The primary effects of earthquakes are ground shaking, ground rupture, landslides, tsunamis, and liquefaction. Fires are probably the single most important secondary effect of earthquakes.

There are two types of earthquakes: tectonic and volcanic earthquakes.

Earthquakes usually cause severe damage to urban centres, resulting in the loss of life and damage to homes and other infrastructure. Although risks are normally associated with cities, the effects on the rural sector and farming communities can be devastating.

why are earthquakes dangerous? The damage caused by earthquakes is from ground shaking, ground rupture, landslides, tsunamis, and liquefaction. Earthquake damage from fires is the most important secondary effect.

Japan

The effects from earthquakes include ground shaking, surface faulting, ground failure, and less commonly, tsunamis.

We cannot prevent natural earthquakes from occurring but we can significantly mitigate their effects by identifying hazards, building safer structures, and providing education on earthquake safety. By preparing for natural earthquakes we can also reduce the risk from human induced earthquakes.

Why are big earthquakes so hard to predict? Reliable predictions require precursors – some kind of signal in the earth that indicates a big quake is on the way. The signal has to happen only before large earthquakes and it has to occur before all big quakes.

Surface waves They are typically generated when the source of the earthquake is close to the Earth’s surface. Although surface waves travel more slowly than S-waves, they can be much larger in amplitude and can be the most destructive type of seismic wave.