continental drift

                     
                                                   CONTINENTAL DRIFT


Until 1912 people used to think that god created the Earth and that the 5 continents and the 5 oceans have been always there.

Wegener was a german meteorologist. He said that all the continents were in the same mass of continent, he called it pangea. But by the time they saw that the continents were sepearing from each other.

The reason was in the underground. There was a mantle that it was very hot. It smelt the rocks and because of that the rocks went up. This produced the movement of the plates

Wegener found different facts to explain his theory:

-Among the fosils of plants and animal species that scientists found since 19th century in different continents some of them were very similar.

-He saw that if they got together all the continents the rest of the glaciers that there were in the continents fit with each other.

-He saw that all the continents together  made a puzzle. Firstly, he saw that it didn't fit because it was irregular but finally he saw that it fit.

We have 15 principal plates in the Earth some of them are biggers than the others. Most of them they are mixed plates they have oceanic lithospheres and continental lithospheres but we have also the pacific plate that is only formed by the pacific oceans it hasn’t any continental lithosphere .

We have three type of waves but the waves p and the wafev s are the most important. Ondas P moves in horizontal and waves S moves in vertical.

The waves rayleight and love waves are the third type of waves.  The first one move like a sea wave and the second one moves like a snake.

This waves cause different reliefs in the our Planet, MOUNTAINS RANGES, ISLANDS AREAS,OCEAN RIDGES, VOLCANOES… But these process are too slow for our life time so we can’t see them, but we know that there is a constant movement that change our planet day by day.

The mountains are formed when two continental plates crash strongly, they are not heavy enough to immerse they just push its other. The sediments of these plates are accumulated forming a big relief what we call mountains . Through the years the mountains can get bigger and bigger, what is happening now in Himalaya.
Subduction. This is when one continental or ocean plate hit one ocean plate. The oldest or heaviest one goes under the ocean plate. This causes different estructures: when both are ocean plates this made island arc; for example, Mariana island. The other one is when one is contiental and the other one is ocean, this causes volcano mountains; for example, los Andes.

The volcano is a way that the Earth use to expel heat and some gases. When the magma goes up to the lithosphere it creates a magma chamber that push the surface and forms the volcano where the lava is emerged. This relief is usually found where tectonic plates are converging or diverging. We also can found underwater volcanoes that often create islands like Hawaii.
NATURAL DISASTERS:

An earthquake is the shaking of the surface of the Earth which can destroy big buildings and kill thousands of people. They are measured by seismometers, according to the local magnitude scale magnitude 3 is almost imperceptible and magnitude 7 can cause serious damages. The largest earthquake in historic time have been of magnitude over 9, in Japan.

A tsunami , also known as a seismic sea wave, is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean. Tsunamis generally consist of a series of waves with periods ranging from minutes to hours. Wave heights of tens of meters can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous and they can affect entire ocean basins


A volcano apart from expelling magma it can also create big clouds that cause chemical reactions which damage the stratosphere and can destroy ozone. For example the biggest volcano of Iceland had created a really big black cloud in 2010 that led to air travel disruption northwest Europe for six days and 800 people were evacuated.

SEISMIC RISKS:

Every day around 25 earthquake happen in the Earth, but most of them are of low magnitude. But the areas where there is a big risk of seismic activity are in the sides of tectonic plates and they formed what is called the ring of fire.

Because of alll this facts that we explained  in the future there will be a different map. For example,we are going to be further from USA