Crust, the upper layer of the Earth, is not always the same. Crust under the oceans, called oceanic crust, is mu thinner than continental crust. It is only about 5 km thick while continental crust can be up to 65 km thick. Also, the two types of crust are not made of the same materials. Oceanic crust is made of a denser collection of minerals than continental crust.The tectonic plates are made up of the Earth’s crust and the upper part of the mantle layer underneath. Together the crust and upper mantle are called the lithosphere and they extend about 80 km deep. The lithosphere is broken into giant plates that fit around the globe like puzzle pieces. These puzzle pieces move a little bit each year as they slide on top of a somewhat fluid part of the mantle called the asthenosphere.