5.3 tectonic plate theory

  1. What is the core made from?

The Earth's core is composed primarily of a solid inner core and a liquid outer core, made mostly of an iron-nickel alloy, with about 85% iron and 10% nickel by weight. The remaining 5% is composed of lighter elements such as sulphur, oxygen, carbon, and silicon. The inner core is a massive, 2,500 km wide solid ball of iron and nickel due to extreme pressure, with temperatures reaching 5,000°C–6,000°C. The outer core is a 5,150 km deep liquid layer of iron, nickel, sulphur, and oxygen. The movement of this liquid metal creates the Earth's magnetic field.

  1. Why is it hot?

The Earth's core remains extremely hot, over 5,000°C, primarily due to residual heat from the planet's formation 4.5 billion years ago, friction from dense materials sinking to the centre, and the continuous radioactive decay of elements like uranium, thorium, and potassium

  1. What are hot spots?

Hot spots are fixed, intensely hot plumes of magma rising from deep within the Earth’s mantle, often far from tectonic plate boundaries

  1. What is the difference between the lithosphere and the aesthenosphere?

The lithosphere is Earth's rigid outer shell that forms tectonic plates, while the asthenosphere is the weaker, hotter, flowing layer beneath it, allowing those plates to move, driven by convection currents

  1. List some of the evidence showing that the earth was once one ‘supercontinent’?

Continents fitting together like puzzle pieces, identical fossils (dinosaurs, plants) found on widely separated landmasses, matching geological formations (mountain chains, rock types) across oceans, and patterns in ancient climate indicators and rock magnetism

  1. Describe how plates move using the points below.

 

  1. Gravity slide

Tectonic plates are elevated at mid-ocean ridges, creating a slope that allows the force of gravity to push the plates downhill away from the ridge

  1. Slab pull

When cold, dense oceanic lithosphere sinks into the mantle at subduction zones due to gravity. As the dense edge plunges, it acts as a slab that drags the rest of the plate behind it, similar to a heavy chain falling off a table.

  1. Ridge push

Gravitational force moves tectonic plates away from mid-ocean ridges. As hot, less-dense magma rises and forms new, elevated crust, this elevated material pushes the older, colder, and denser oceanic plate down the slope, acting as a force that drives seafloor spreading.

Plate Collision: two tectonic plates, often continental plates, move towards each other.

Compression: the immense pressure at the collision zone causes the rocks and sediments between them to be squeezed.

Folding: instead of breaking, the rock layers (strata) bend and fold, similar to how a rug folds when pushed.

Uplift: this folding process pushes the land upwards, creating high peaks and long mountain chains.