Plate tectonics The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction.
This theory was developed by Alfred Wegener. Wegener believed that all of the continents were connected as one large land mass (he called Pangaea) about 200 million years ago.
The theory of plate tectonics states that the earth’s outermost layer, is broken into 7 large rigid pieces called plates: the African, North American, South American, Eurasian Australian, Antarctic, and pacific plates. Several minor plates also exist. These plates fit together like a jigsaw puzzle. The plates consist of two types of crust: continental crust and oceanic crust. The theory explains the movement of the earth’s plates and the cause of earthquakes, volcanoes, oceanic trenches, mountain ranges and many other geologic phenomenon. Convection currents and gravitational forces cause the plates to move. There are three types of plate movements. Plate tectonics
Evidence to support the theory Wegener’s Evidence Wegener’s summary was based on a number of careful observations: The rocks match The physical fit between the continents The fossil evidence The plants and animals match
Two types of crust The plates consist of two types of crust: The continents are made up of continental crust The oceanic crust are the plates beneath the oceans.
What cause the plates to move? l Convection Current and gravitational forces within the mantle cause the plate to move.
Convection current l Convection Current is the driving force of plate tectonics in which hot, plastic-like material from the mantle rises to the lithosphere, moves horizontally, cools, and sinks back to the mantle. l The convection currents provide enough energy to move the plates in the lithosphere.
Three type of plate movements The plates are all moving in different directions and different speeds (from 2cm to 10 cm per year which is about the speed at which your fingernail grow) in relationship to each other. The place where two plates meet is called a plate boundary. Boundaries hav different names depending on how the two plates are moving in relationship to each other. The three types of plate boundaries are: Divergent: plates move away from each other (tension) (New crust is made. Convergent: plates move towards each other (compression) Mountain building (Himalayas) Transform or lateral : plates horizontally grind against one another (strike-slip motion) (Shallow earthquakes, Andreas Fault)