Lithospheric Plates and the Earth's Crust

The Earth's crust and the upper part of the mantle make up the lithosphere. It is divided into large plates.

Structure of the Earth

• From the center to the surface, the Earth consists of: the core (solid inner part, liquid outer part), the mantle, the Earth's crust.
• Thickness of the crust: 30-70 km under the continents, 5-10 km under the oceans.

Rocks

Group	Examples
Igneous	granite, basalt
Sedimentary	limestone, sandstone
Metamorphic	marble, gneiss

• Marble and gneiss: metamorphic rocks.
• Granite and basalt: igneous rocks, they form when magma cools. Limestone and sandstone are sedimentary rocks.

Lithospheric plates

• Major plates: Eurasian, African, North American and South American, Pacific, Indo-Australian, Antarctic.
• When plates move apart (mid-ocean ridges) or collide, mountains, earthquakes and volcanoes appear.
• The Himalayas: Indo-Australian + Eurasian.
• The area surrounding the Pacific Ocean is called the "Ring of Fire".

Earthquakes

• Hypocenter: the focus of an earthquake (underground).
• Epicenter: its projection on the Earth's surface.
• Marble is not a sedimentary but a metamorphic rock. Limestone is transformed into marble.

1. The earthquake focus is underground (hypocenter)
2. Waves rise to the surface
3. The strongest shaking is at the epicenter