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Social studies: Obj. We will talk about different cultures in diffrent parts of the world and we will also Continue talking about tectonic plates.


Plate tectonics (from the Late Latin tectonicus, from the Greekτεκτονικ?ς"pertaining to building")[1] is a scientific theory which describes the large scale motions of Earth's lithosphere. The theory builds on the older concepts of continental drift, developed during the first decades of the 20th century (one of the most famous advocates was Alfred Wegener), and was accepted by the majority of the geoscientific community when the concepts of seafloor spreading were developed in the late 1950s and early 1960s. Thelithosphere is broken up into what are called tectonic plates. In the case of the Earth, there are currently seven or eight major (depending on how they are defined) and many minor plates. The lithospheric plates ride on theasthenosphere. These plates move in relation to one another at one of three types of plate boundaries: convergent, or collisional boundaries; divergentboundaries, also called spreading centers; and conservative transformboundaries. Earthquakesvolcanic activitymountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative movement of the plates varies, though it is typically 0–100 mm annually.[2]