PTR - The Lithosphere Lesson
The Lithosphere
Above the ductile asthenosphere is the more rigid lithosphere. The lithosphere is the outermost, solid layer of the Earth, but it is not all in one piece. It actually resembles an orange peel that was removed in pieces and then glued back together (a baseball is another good analogy, as the covering of a baseball is made of several pieces that have been stitched together). Each of these pieces is known as a tectonic plate. Tectonic plates can be large or small and can consist of sections containing continents or not.
The fifteen main plates that cover the Earth are the North American, Caribbean, South American, Scotia, Eurasian, African, Arabian, Indian, Australian, Antarctic, Pacific, Filipino, Nazca, Cocos, and Juan de Fuca plates.
Complete the tectonic plates activity below:
Plates that contain continents are known as continental plates, while those that do not are known as oceanic plates. Oceanic plates are made primarily of basalt, a dark igneous rock formed when magma cools quickly. The "continent" portions of continental plates contain large amounts of granite, which forms when magma cools slowly (Stone Mountain in Atlanta is an example of a granite extrusion). Granite is less dense than basalt (2.7-2.8 g/cm3 vs. 2.9 g/cm3) and contains a larger amount of silica (73% vs. 53%).
Since the lithosphere sits on top of the asthenosphere, the convection currents underneath the tectonic plates push them much in the same way that a cracker would float across the surface of a pot of boiling soup (for those of you into "mosh pits" at concerts, think of "crowd surfing", with the "surfer" being the tectonic plate and the people underneath acting as the asthenosphere). As these plates are pushed around, they interact with the other plates covering the Earth. Depending on the types of plates involved and the directions that they are moving, several different boundaries and land formations can result.
IMAGES CREATED BY GAVS OR OPENSOURCE