Tectonics - Hazardous Earth

Starting from the center, what is the Earth’s structure?

Starting from the center, what is the Earth’s structure?

• Inner core

• Outer core

• Lower mantle

• Upper mantle (the asthenosphere)

• The lithosphere

• The crust (the top of the lithosphere)

What is the deepest artificial point on Earth?

The Kola Superdeep Borehole in the Pechengsky District, Russia

Explain the inner core?

• Solid ball

• Made of Iron and Nickle

• Under high amount of pressure - as it has the weight of the Earth pushing against it

• Within it, radioactive elements like uranium and thorium are decaying. Radioactive decay gives off heat. This heat is responsible for the Earth’s internal energy and it spreads through the different layers

• 5000 degree celsius

What causes the inner core to remain solid?

the fact that it has the pressure of the Earth pushing on it.

What is responsible for the Earth’s internal energy

The heat that is given from the radioactive element decaying in the inner core of the Earth

Explain the outer core?

• Molten (liquid) layer

• Iron and Nickle

• Surrounds the inner core

• Heat from the inner core creates convection currents in the outer core, which transfers heat to the mantle above

Explain the mantle?

• Largest layer

• Solid rock apart from the very top where it behaves like a dense fluid

• Top layer is known as asthenosphere

• Asthenosphere constantly moves and flows due to convection current, which moves the solid lithosphere above

Explain the lithosphere

• Solid rock that lies on top of the asthenosphere

• Majority of the lithosphere is technically in the mantle, but the very tpo of the lithosphere is the Earth’s crust

• The crust is split into multiple large slabs called tectonic plates

• The crust is either continental or oceanic

• Plates move due to movement of the liquid asthenosphere

What is continental crust?

Crust that makes up our land (ols, less dense and thick)

What is oceanic crust?

• Makes up the ocean floor

• Younger but still very old, dense and thin

Why do plates move?

They move due to the movement of the liquid asthenosphere.

Where do convection current occur?

Within the upper mantle (asthenosphere)

Explain how convection currents happen?

• Energy from radioactive decay in the core heats up the fluid asthenosphere

• The hot liquid is less dense than its surroundings, so it rises upwards

• When it reaches the top, it cools and becomes more dense, and therefore sinks back down to the bottom

• It is heated up again, and the cycle continues

• The plates, which lie on top, are pushed and pulled by the convection currents in the asthenosphere

What is the lithosphere divided up into?

• Continental crust

• Oceanic crust

What is the depth of the continental crust

0-100km thick

usually 30-50km thick

What is the depth of the oceanic crust

usually 6-8km thick

What is the physical state of the continental crust

solid

what is the physical state of the oceanic crust?

solid

What is the density of the continental crust

2.7

What is the density of the oceanic crust?

3.3

What is the composition of the continental crust

Rocks similar composition to granite

What is the composition of the oceanic crust?

Rocks similar to basalt

What is the temp of the continental crust?

air temp 900

What is the temp of the oceanic crust?

air temp is 900

What is the mantle divided up into?

• Asthenosphere

• Lower Mantle

What is the depth of the asthenosphere?

Starts anywhere from 35-250km to 700km

What is the depth of the lower mantle?

700-2900km

What is the physical state of Asthenosphere?

Partially molten/fluid

What is physical state of the lower mantle?

Solid

What is the density of the asthenosphere?

3.4 - 4.4

What is the density of the lower mantle?

4.4 - 5.6

What is the composition of the asthenosphere?

Silicates (made of silicon)

What is the composition of the the lower mantle

Silicates (made of silicon)

What is the temp of the asthenosphere?

900 to 1600

temp of the lower mantle?

1600-4000

What is the core divided into?

• Outer core

• Inner core

What is the depth of the outer core

2900km - 5270km

What is the depth of the inner core?

5270km - 6370km

What is the physical state of the outer core

liquid

What is the physical state of the inner core?

Solid

density of the inner core?

12.6 - 13.0

density of outer core?

9.9 - 12.2.

composition of outer core?

iron and nickle

composition of inner core

iron and nickel

temp of outer core

4000 - 5000 degrees

temp of inner core

• around 5400 degrees

What is a plate boundary?

It is where the plates meet.

How long has plate tectonic movement been happening ?

Hundreds of millions of years

Explain the continental drift theory in detail?

• By Alfred Wegener

• in the early 20th century

• suggest that the Earth's continents were once joined together in a single supercontinent called Pangaea.

• Over time, these continents gradually drifted apart and moved to their current positions.

• Wegener supported this theory with evidence such as:

  • the fit of the continents

  • matching geological formations

  • similar fossil records across different continents

• The theory was met with skepticism due to a lack of credibility.

• It was later supported by the discovery of plate tectonics, which explained that the Earth's lithosphere is divided into several large plates that float on the semi-fluid asthenosphere

• The continental drift theory revolutionised our understanding of Earth’s geological history

What was the evidence for the continental drift theory?

• the fit of the continents

• matching geological formations

• similar fossil records across different continents

Give an example of a plate that is continuously moving?

• The atlantic ocean is growing as the USA is moving away from the UK about 2-5 cm a year

Name all the tectonic plates ?

There are several major tectonic plates on Earth, including:

1. African Plate

2. Antarctic Plate

3. Australian Plate

4. Eurasian Plate

5. North American Plate

6. South American Plate

7. Pacific Plate

8. Indian Plate

9. Arabian Plate

10. Caribbean Plate

What are the types of plate boundary?

• Divergent

• Convergent/Destructive

• Conservative

What is the divergent plate boundary?

Plates move away from each other

Explain what happens at a divergent plate boundary?

When the two plates are pulled apart, magma rises in between the gap left by the two plates separating. Lava then pours out onto the surface.

Volcanoes form in the areas where lava pours out. This lava is usually runny and free-flowing, which creates flatter volcanoes. Earthquakes also occur here as the plates shake and vibrate when they move apart. This process can happen on continental crust or oceanic crust .

In the ocean:

• new land is formed - sea floor spreading

in the land:

when the lava cools, it form rocks. Over time the rocks build up and can form islands e.g. Iceland

What can be found at a divergent plate boundary?

• Earthquakes

• Volcanoes

What kind of volcanoes can be found at divergent plate boundaries

Flatter volcanoes

Why can earthquakes occur when there is a divergent plate boundary?

Because the plates shake and vibrate as they move apart

What type of crusts can a divergent plate boundary be on?

• continental

• Oceanic

What is sea floor spreading?

Sea floor spreading is the process by which new oceanic crust is formed through volcanic activity at mid-ocean ridges. As magma rises to the surface, it cools and solidifies, creating new crust. This process pushes the existing crust apart, causing the sea floor to spread and the continents to move. It is a key component of plate tectonics and helps explain the movement of Earth's lithospheric plates.

What is a rift valley?

On continental crust, a divergent plate boundary causes huge fractures in the land, creating a low land region known as a rift valley

What is a famous rift valley?

The East African Rift Valley

Explain the East African Rift Valley

The rift zone stretches for thousands of kilometres down East Africa, and many volcanoes have historically been present in this area. If the divergent plate boundary continues on its path, the East of Africa may eventually split off from the rest of mainland Africa, and will be separated by sea.

What is a convergent/destructive plate boundary?

When the plate move towards each other

Explain what happens at destructive or convergent plate boundary

This is when the plate move towards each other. This causes one of the plates to subduct (sink) below the other into the mantle, where it is destroyed.

Give an example of a convergent plate boundary?

For example, the oceanic crust is moving towards continental crust. This is happening off the west coast of South America where the Nazca Plate is subducting below the South American Plate.

What processes must happen for a convergent or destructive to cause earthquake and volcanoes?

• The denser oceanic crust is subducted below the continental crust

• The plate that is subducting leaves a deep ocean trench

• Friction between the two plates causes strong, deep earthquakes

• The oceanic crust is melted as it is pulled deeper into the mantle, creating magma.

• This magma causes pressure to build up under the crust.

• Eventually the magma pushes out through weaknesses in the crust, creating explosive volcanoes.

Explain destructive or convergent plate boundaries between two oceanic crust?

Where the denser plate sinks below and islands in the ocean can form.

Give an example of convergent plate boundaries between two oceanic plates?

The Mariana trench

Explain destructive or convergent plate boundaries between two continental crust?

When two continental plates meet, neither plate can subduct below the other. The crust is instead crumpled upwards by the pressure building between two plates, creating fold mountains.

Give an example of two continental plates meeting at a destructive plate?

An example of this is the Himalayas, which formed due to the Indian Plate and Eurasian Plate colliding.

What landforms can be seen in when two continental plates meet at a destructive boundary?

Folding Mountains

What is a conservative plate boundary?

Parallel plates move in different directions or at different speeds in relation to each other

Explain what happens a conservative plate boundary?

At a conservative plate boundary, parallel plates move in different directions or a different speeds in relation to each other. When these plates move side by side, friction builds between the plates. The friction builds up over many years, and eventually the pressure becomes so large that the plates eventually move in a sudden jolt.

This releases a lot of energy which send vibration through the ground. This is an earthquake

On oceanic crust, this movement can displace a lot of water, which cause large waves called tsunamis.

On continental crust, fault line can occur where the ground is cracked by the movement.

There are no volcanoes on conservative plate boundaries because no magma is being generated.

What is a hotspots?

Hotspots are area of volcanic activity that are not related to plate boundaries.

Explains what happens at a hotspot?

Hot magma plumes from the mantle rise and burn through weaker parts of the crust. This can create volcanoes and islands. The plume stays in the same place but the plates continues to move, which sometimes causes a chain of island.

What landforms can form at hotspots?

• Volcanoes

• Islands

Give an example of a chain of islands

Hawaii

Explain Volcanoes on Divergent plate boundaries

• Non - explosive

• Runny, fast flowing lava - made up of basalt (very hot and has low viscosity (thickness))

This creates shallow sided (flat) shield volcanoes.

Explain Volcanoes on convergent plate boundaries

• Very explosive - due to the high pressure the magma is under

• Hot gas, ash and rock is spewed from the volcanoes

• Fast, extremely hot clouds of gas, ash and debris can roll down the side of the volcano in a pyroclastic flow

• Lava is made of andesite - causing it to be viscous and very slow flowing

Steep sided composite volcanoes are formed from these eruption

What is a pyroclastic flow?

A pyroclastic flow is a fast-moving mixture of hot gas, ash, and volcanic rocks that flows down the slopes of a volcano during an explosive eruption. It can reach speeds of hundreds of kilometers per hour and is extremely dangerous, capable of destroying everything in its path.

Explain earthquakes on divergent?

• Smaller earthquake - less built up friction

Explain earthquakes on Conservative Boundaries?

• Very destructive and intense

• If an earthquake is shallow, the earthquake can cause very intense shaking, which can bring down buildings, break pipes and destroy infrastructure

Explain earthquakes on convergent Boundaries?

• Very strong.

• These earthquake can be very severe, especially if they are shallow.

What is the Richter Scale?

The Richter Scale is the scale that seismologists use to measure the strength on an earthquake. The scale is logarithmic, which means each number is 10x bigger than the last and approximately 31.6 times more energy released. The scale ranges from 0 to 10,

What is tsunamis?

Earthquake can trigger huge waves of seawater to travel across the ocean and hit a coastal area. This large wave is known as a tsunami, and can cause extreme flooding and damage to property.

Explain the formation of tsunamis?

• When an oceanic crust is jolted vertically during an earthquake, all of the water above this plate is displaced.

• The water travels fast but with a low amplitude (height). Larger waves began rippling across the ocean away from the earthquake’s epicenter

• As it gets closer to the coast, the sea level decreases so there is friction between the sea bed and the waves.

• This causes the waves to slow down and gain height, creating a wall of water that is on average 10 feet high, but can reach 100 feet.

What is the anatomy of a tsunamis?

• The tsunami formed when an earthquake vertically shifted the seabed by several meters

What is a composite volcano?

A composite volcano, also known as a stratovolcano, is a tall and steep-sided volcano formed by alternating layers of lava flows and pyroclastic materials. These volcanoes are characterized by their explosive eruptions and can be found in subduction zones where tectonic plates collide.

What are some examples of composite volcanoes?

Examples of composite volcanoes include Mount Fuji in Japan and Mount St. Helens in the United States.

What is a shield volcano?

• A shield volcano is a type of volcano characterized by its broad, gently sloping shape and built-up layers of basaltic lava flows.

• It is formed by the eruption of low-viscosity lava that spreads out in all directions, creating a wide, shield-like structure.

• Shield volcanoes are typically not very explosive and are associated with hotspots and divergent plate boundaries.

Examples of shield volcanoes?

Examples of shield volcanoes include Mauna Loa in Hawaii and the Galapagos Islands.