LA LITOSFERA

María Jesús Camposlearningfromgeography.wikispaces.com

LithosphereIt comes from the ancient Greek “lithos” which means stone and “sphaira” which means sphere.

It refers to the solid rocky crust that covers the Earth.

The crust is composed of minerals.

The Crust

The crust is a solid layer that floates over the mantle’s magma.It represents 1% of the Earth’s volume but it has different thickness and length.

The crust is divided into tectonic plates that move over the mantle.

The crust presents different shapes, lenghts, etc. Some times it appears under the oceans and others over the sea surface. This is called the Earth’s relief.

The shapes of the Earth’s relief changes thanks to internal forces and external agents.

Continental drift and tectonic plates

200 million years ago all the continents were united into a single supercontinent called Pangea.

Pangea broke up because of the internal forces of the mantel and the tectonic plates gradually moved apart. This theory is called continental drift.

Tectonic plates slide against each other or move apart. Thus, the plate’s boundaries are unstable.

Internal Forces of Relief

Internal forces and pressures from the mantle causes the crust to:

Fold: are deformations of the Earth’s surface where rock layers bend.

Fault: are breaks in rock layers wher the rock is too hard to bend.

Subducts: when one rock layer from a plate sinks under the other and its materials melts into the mantle’s magma.

Sometimes this pressures apperar in the form of :

Earhtquakes:they happen when energy is released in seismic waves from a focus or hypocentre inside the Earth usually when the boundaries of the plates slide against each other.

Volcanoes: are cracks on the Earth’s crust and magma from the mantle erupts ro the surface and solidify creating new crust.

External Agents of Relief

The external agents that shape the Earth’s surface are: Water Wind Vegetation

They erode relief breaking it up and transporting and depositing eroded materials on a different place.

Although human beings are not natural agents they also modify relief.

Relief The crust presents different shapes, lenghts,

etc. Some times it appears under the oceans and others over the sea surface. This is called the Earth’s relief.

The Earth’s relief comprises the forms and shapes of the Earth’s surface.

Relief Sometimes the Earth’s

crust appears over the sea surface and other times under the sea surface.

Over the sea surface there are 6 continents: Africa Europe América Asia Oceania Antarctica

The North Pole is not a continent because it is formed by frosted water.

Continents are separated by oceans or seas: Pacific Ocean Atlantic Ocean Indian Ocean Artic Ocean Antartic Ocean or

Southern Ocean Mediterranean Sea Read Sea

Continental Relief Mountains: High

elevations of the Earth’s surface. When they are grouped together it is called range.

Plateau: high flat areas that are formed from eroded mountains.

Plain: low flat areas. Alluvial plains are formed by rivers and coastal plains are near the sea.

Basins: very low areas sometimes below sea level.

Valley: elongated lowland between ranges of mountains or hills.

Península: land mass entirely surrounded by water except in one part connected with the mainland which is called isthmus.

Island: a land mass entirely surrounded by water.

Cape: part of the coast that projects into the sea.

Relief on the Ocean Floor Gulf: large area of a sea

or ocean partially enclosed by land.

Bay: small area of a sea or ocean partially enclosed by land.

Ría: long narrow inlet of the seacoast in which the sea occupies the mouth of the river.

Continental shelf: great underwater plateau which correspondt to the border of a continent and is usually less than 400 metres deep.

Continental slope: the descent from the continental shelf to the ocean bottom.

Abyssal plain: huge under water plains that have an extension between 3000 and 7000 metres deep.

Ocean trench: long valley on the ocean floor that can have 11000 metres deep.

Ocean ridge: underwater mountain ranges.

Created by María Jesús CamposChusteacherWikiteacher