Earth and science 100% please!

List the Earth's layers from outermost to innermost.

Crust (5–70 km) → Upper Mantle → Lower Mantle → Outer Core (liquid) → Inner Core (solid, 5100–6371 km deep).

What are the lithosphere, asthenosphere, and mesosphere?

Lithosphere: rigid crust + top mantle (0–100 km). Asthenosphere: semi

How do temperature and pressure change with depth?

Both increase. ~30°C per km. Inner core reaches ~6000°C and ~3.5 million atm pressure.

Compare oceanic and continental crust.

Oceanic: 5–10 km, basalt, dense (~3 g/cm³), younger (~200M yrs). Continental: 30–70 km, granite, lighter (~2.7 g/cm³), older (>4B yrs).

What causes plate movement?

1. Convection currents (core heat → mantle rise & sink) 2. Ridge push (new crust at ridges pushes plates) 3. Slab pull (subducting plate sinks, drags crust).

Summarise plate tectonic theory.

Earth's lithosphere is split into 7 major plates moving over the asthenosphere. Movement causes quakes, volcanoes, trenches, mountains.

What is subduction? Give examples.

Dense oceanic crust sinks under lighter continental crust. Creates volcanoes/trenches. E.g., Nazca Plate under South America → Peru

What happens at divergent boundaries?

Plates move apart. Magma rises. Forms: mid

What happens at convergent boundaries?

Plates collide. One subducts. Forms trenches (e.g. Mariana), mountains (e.g. Himalayas), volcano arcs (e.g. Andes).

What happens at transform boundaries?

Plates slide past. No crust formed/destroyed. Frequent quakes. Example: San Andreas Fault, California.

Who was Alfred Wegener and what did he propose?

In 1912, Wegener proposed all continents were once joined as Pangaea and drifted apart.

What evidence supported Wegener’s theory?

1. Fossils (Mesosaurus in S.America/Africa) 2. Glacial grooves match 3. Rock strata align 4. Continents fit like puzzle.

Why was Wegener’s theory rejected?

Lacked a mechanism for movement. Seafloor spreading and convection later proved it.

What is seafloor spreading?

New oceanic crust forms at mid

What technologies proved plate movement?

Sonar (seafloor mapping), seismographs (quakes), GPS (track movement), magnetometers (magnetic reversal patterns).

What is an earthquake?

A sudden release of stress along a fault. Sends seismic waves through Earth.