Pangaea

1. Pangaea The Pangaea theory is one that states that all present continents were once together and collectively known as a 'supercontinent' called a Pangaea. The word 'Pangaea' means 'all lands' in Greek, accurately defining the way the continents were 200 millions years ago before it split up. These split-up pieces drifted slowly apart and became the way they are today. Even until now, the shape of the Earth surface is still changing, and it will be forever, as long as the mantle underneath the Earth's crust gets heated and convection currents in the magma keeps dragging the plates. The Pangaea theory was treated with much skepticsm when it was first raised. But since then, there have been much evidence to support this theory.

3. Tectonic Forces There are two types of tectonic forces that build or shape the landscape. One is Volcanism. Volcanism had alot to do with forming the Earth’s crust. Pressure may cause molton rock to rise to the surface of the crust. These extrusions (magma which cools on the earths surface) may create a violent volcano, or spread gently over the countryside. This all depends on the amount of pressure that has built up, and the force of the extrusion.

4. Volcanoes have been very active throughout the history of the cordillera, as most of the western Cordillera was formed through lava flows. The Canadian Shield and the Appalachians have also had a history of Volcanoes, but only the Cordillera has volcanoes that aren’t active but may become active (dormant). • The core of the coastal ranges are an example of this. Sometimes lava doesn’t reach the surface, but is forced between layers of rock called Strata. This is called intrusion. This process will sometimes cause surface rock to rise. • The other type of tectonic force that shapes the earth, does by exerting powerful stresses and strains in the crust itself. The crust is constantly in a very slow motion. It floats on the semi-liquid molten maga below it. Movement in the mantel shifts the continental plates.

5. Sometimes tension in layers pushes rock together and forces them upward. If the magma underneath flows away, the rock may fall making a depression. The rock layers may begin to fold in order to relieve pressure. This can cause folded hills, or mountains to form. The Appalachians are an example of this. • As the strata is being pulled in different direction, cracks (called joints) may form. Often there is movement along a joint or set of joints, this is called faulting and the joint is known as a fault. • When there is action or movement along these faults, and earthquake can occur. The greater the movement the more intense the earthquake.