Pangaea, Boundaries, and Earth Plates: by Journey Winkle
There are 3 different types of plate boundaries, convergent, divergent, and transform. The three plate boundaries describe how an Earth plate moves. Earth plates move because they float on the magma part of the lithosphere, drifting very, very slowly. There are two different kinds of plates, oceanic plates and continental plates. oceanic plates have oceans on top of them and continental plates have land on them. I'm going to describe the 3 different types of plate boundaries first.
When a plate boundary is convergent, it means the 2 plates that make up the boundary are moving towards each other. 3 different things can happen when two plates collide. When a continental crust collides with an oceanic plate, the oceanic crust, which is more dense, will sink below the continental crust. The place where this happens is called a subduction zone. The oceanic plate goes deep down into the Earth, until it gets so hot that the plate melts and comes up as magma. The magma can hit hot spots in the Earth and cause the pressure to become so great they come out of the Earth in volcanoes, which causes volcanic eruptions. When an oceanic crust collides with another oceanic crust, the older, more dense plate sinks beneath the other one and what happens after that is similar to what happens when a continental crust collides with an oceanic crust. When a continental crust collides with another continental crust, neither goes beneath the other. They both keep moving forward at each other and create folds in the crust, which makes mountain ranges. The Appalachian, Andes, and Himalaya mountain ranges were made this way.
When a plate boundary is divergent it means the plates that make up the boundary are moving away from each other. When two continental plates are divergent they produce rifts, which can become rift valleys. When two oceanic plates are divergent they form a mid-oceanic ridge. Lava can come up through the hole that the divergent plates make and cool into crust to make volcanic islands. It is predicted that Africa will soon split into two different landmasses because there is a divergent plate boundary in East Africa.
When a plate boundary is transform it means the two plates that make up the boundary are scraping along each other in opposite directions. Neither plate will stop moving, so when they get stuck on a protrusion of the other plate's, the plate keeps pushing until they burst past it, causing a release of energy which moves through the Earth as an earthquake. This is the case with the Pacific and North American plates, and this causes California's many earthquakes.
The Pangaea theory is that the continents used to be one huge landmass called Pangaea. The plates, with the continents on top, moved with the plates underneath who were moving apart. The continents spread out until they came into the shape we know today. The continents are still moving apart very slowly, and eventually they will be in different positions.