The Structure of the Earth and Plate Tectonics

Flashcards covering the internal layers of the Earth, crust types, continental drift, mantle convection currents, and plate boundary interactions.

What are the three main layers of the Earth's internal structure from the surface downwards?

The crust, mantle, and core (which is further divided into the inner core and outer core).

What is the SIAL or granite layer and what are its characteristics?

It is the layer that forms the continents. It is made up of silica and aluminium, is not a continuous layer, and is less dense, allowing it to float above the SIMA layer.

What is the SIMA or basaltic layer and what are its primary elements?

It forms the ocean floors and is primarily made up of silica and magnesium.

What is the name of the layer that separates the crust from the mantle?

The Mohorovicic discontinuity.

What are the primary features, depth, and rock composition of the mantle?

The mantle lies below the crust, has a depth of about $2900\,\text{km}$, is the thickest section of the Earth, and contains convection currents. It is made of olivine rocks (a combination of iron and magnesium) and hot liquid rocks called magma.

What is the name of the boundary that separates the mantle from the core?

The Gutenberg discontinuity.

What are the alternative names for the core and what minerals compose it?

The core is also known as the barysphere or NIFE. It is the heaviest layer of the Earth and is made up of nickel (NI) and iron (FE) minerals.

What are the characteristics, state, and temperature of the Earth's outer core?

The outer core is believed to be liquid, largely made up of iron and nickel, and extremely hot with temperatures up to $5500\,\text{degrees centigrade}$.

What are the characteristics, state, depth, and temperature of the inner core?

The inner core is believed to be solid due to immense pressure. It is located at the centre of the Earth, about $6340\,\text{km}$ from the surface, with temperatures of about $5500\,\text{centigrade}$.

What is the theory of plate tectonics?

It is the theory that the Earth's outer shell or crust is divided into several small, irregularly shaped plates (slabs of solid rock) that float on and over the mantle.

What are the seven major or primary tectonic plates?

African, Eurasian, North American, South American, Pacific, Indo-Australian, and Antarctica.

What are the seven secondary tectonic plates?

Nazca, Cocas, Caribbean, Scotia, Arabian, Philippine, and Juan de Fuca.

How do oceanic crust and continental crust differ in age, thickness, density, and weight?

Oceanic crust is younger, thinner, denser, and heavier, whereas continental crust is older, thicker, less dense, and lighter.

How did the supercontinent Pangea divide according to the theory of continental drift?

Convection currents moved Pangea apart into two supercontinents: Laurasia and Gondwanaland, which further separated into current continental land masses.

How do convection currents operate within the Earth's mantle?

Magma near the outer core is heated, expands, and becomes less dense, rising towards the crust. Near the crust, it cools, becomes denser, and sinks, creating circular currents that generate friction and move the crust above.

What are the three general movement zones of plate boundaries?

Convergent zones (plates moving towards each other), divergent zones (plates moving away from each other), and transform zones (plates moving past each other).

What are the four specific types of plate boundaries?

1. Constructive
2. Collision
3. Destructive
4. Conservative

What occurs at a constructive or divergent plate boundary?

Two oceanic plates move apart under the ocean, causing sea floor spreading. Magma escapes from the mantle, cools upon touching the ocean floor, and creates ocean ridges (e.g., Mid-Atlantic ridge) or new islands (e.g., Iceland).

What occurs at a destructive or convergent plate boundary?

Oceanic and continental crusts collide, and the denser oceanic crust subducts under the continental plate. Heat and friction melt the subducting plate to form volcanoes, while the continental plate is pushed up into fold mountains (e.g., Andes in South America) and a deep ocean trench is created.