Plate Tectonics, Earthquakes, and Volcanoes

by Jamie Kim

What are plate tectonics?

Plate tectonics are lithospheric plates.Plate tectonics is the theory that the Earth’s lithosphere is divided into tec-tonic plates that move around on top of the asthenosphere (soft rock).Moving plates cause major changes in a world map over millions of years.

Plate Boundaries

The border between two tectonic plates is a boundary.

What are the 3 types of plate bound-aries?

The 3 types of plate boundaries are: divergent, convergent, and transform.A divergent boundary is when two tectonic plates separate (pull apart).A convergent boundary is when two tectonic plates collide (come to-gether).A transform boundary is when two tectonic plates slide past each other.

Divergent Boundaries

Divergent boundaries diverge. They sepa-rate, and they pull apart from each other.Divergent boundaries cause rift valleys and mid ocean ridges.

Convergent Boundaries

Convergent boundaries converge (collide).Convergent boundaries are often known as subduction zones.When continental crust meets continen-tal crust at a convergent boundary, a col-lision occurs, resulting in folds, faults, and high mountains.

Convergent Boundaries

Transform Boundaries

Transform boundaries are where plates slide past each other. They connect other plate boundaries and are characterized by earthquakes.When transform boundaries produce earthquakes, they are called “strike slips”.

Continental - ContinentalWhen 2 tectonic plates with continental crust collide, they buckle and thicken, which pushes the continental crust upward.When 2 continental crusts collide, they cause mountains. When 2 continental crusts pull apart, they cause rift valleys.Folded Mountains

- Himalaya Mountains - Appalachian Mountains

Oceanic - Oceanic

When 2 tectonic plates with oceanic lithosphere collide, one of the plates with oceanic lithosphere is subducted, or sinks, under the other plate.When 2 oceanic crusts collide, they cause trenches and volcanic islands.When 2 oceanic crusts pull apart, they cause mid ocean ridges and it causes seafloor spreading.

Oceanic - ContinentalWhen a plate with oceanic crust collides with a plate with a continental crust, the denser oceanic crust sinks into the as-thenosphere. This convergent boundary has a special name: the subduction zone. The old ocean crust gets pushed into the asthenosphere, where it is remelted and recycled.Pressure from plates is released.

Continental Drift

Many people think that Earth began with a supercontinent called Pangaea. But, those people are wrong.Pangaea is the most recent succession of supercontinents that have formed, and broken up over time.Continental drift is the drifting away from the supercontinent to the new formation of continents we have today. It is the sin-gle landmass drifting apart.

Stress, Faults, and what it Produces

A convergent boundary’s type of stress is compression. Its type of fault is reverse, and it produces mountain ranges, subduction, and trenches.A divergent boundary’s type of stress is ten-sion. Its type of fault is normal, and it pro-duces seafloor spreading, rift valleys, and mid ocean ridges.A transform boundary’s type of stress is shearing. Its type of fault is a strike slip, and it produces earthquakes.

EarthquakesAn earthquake is a release of pressure. It hap-pens beneath the Earth’s surface.The thinner the crust is, the smaller the earth-quake is.Earthquakes happening in convergent bound-aries are the most EXTREME! Transform boundaries cause strike slip faults.

-A fault is a break in the Earth’s crust.A focus is where the earthquake starts. The epicenter is the imaginary place directly above the focus.

More about Earthquakes!

Earthquakes happen at boundary lines.P - waves are primary waves or pressure waves. They travel through both solids and liquids, and they travel FAST. S - waves are secondary waves. They only travel through solids, and not liquids.Surface waves do the most amount of damage.S - waves and P - waves combined are L - waves. L - waves are land waves and surface waves. Earthquakes represent sudden breaks in crusts that were continuously stressed by plate movement.

How do Earthquake Waves Travel?Seismic waves are waves of energy that travel through the Earth.Seismic waves that travel through the Earth in-terior are body waves. There are two tops of waves: P waves and S waves. Seismic waves that travel along Earth’s surface are called surface waves.Each type of seismic wave travels through Earth’s layers in a different way and at a differ-ent speed.The speed of a seismic wave depends on the kind of material the wave travels through.

P waves

P waves are waves that travel through solids and liquids. They are the fastest seismic waves, so they always travel ahead of other seismic waves.P waves are also called primary waves, because they are always the first waves of an earthquake to be detected.

S waves

S waves are waves that cause particles of rock to move in a side-to-side direction.S waves only travel through solids. S waves are the second fastest seismic waves. S waves are also called shear waves or secondary waves.S waves shear rock side to side, which means they stretch the rock sideways.

Surface WavesSurface waves move along the Earth’s sur-face and produce motion, mostly in the upper few kilometers of Earth’s crust.There are two types of surface waves. One type of surface wave produces motion up, down, and around. The other type pro-duces back-and-forth motion like the mo-tion produced by S waves.Surface waves are different from body waves, because they travel more slowly, and they are more destructive.

Deformation

Deformation is the change in the shape of a rock.A fault is the break in the Earth’s crust. (break in the body of a rock)A fold is the bending of rock layers, due to stress.

VolcanoesSome people think that the mantle is molten every-where, but it’s not. The mantle is solid, but capable of flowing. Only under special conditions, (at hot spots and along plate boundaries) the mantle melts to make magma, which then rises to the surface to cre-ate a volcanic eruption.The Ring of Fire is the collisions of Earth’s tectonic plates that produce earthquakes.Earthquakes and volcanoes are both caused by the movement of tectonic plates.Sometimes, earthquake happenings predict volcano eruptions.For 2 million years, volcanoes have been making new crusts.The gases from volcanoes made the asthenosphere.

More on Volcanoes!

Volcanoes are a vent in the Earth’s sur-face through which magma and gases erupt.Volcanic arcs are arc-shaped chains of volcanoes formed above a subduction zone.There are more than 400 active volca-noes today.

Volcanoes + Climate?!

Catastrophic events, such as volcanic eruptions, can influence climate. Volcanic eruptions send large amounts of dust, ash, and smoke into the atmos-phere.In the atmosphere, the dust, smoke, and ash particles act as a shield. The shield blocks some of the sun’s rays, which causes the Earth to cool.

Thank You for Watching!

Thank you for watching my Power Point Presentation.I hope you enjoyed watching, and I hope you learned something new!