plate tectonics and plate boundaries

• by studying world maps, German geophysicist Alfred Wegener found that the continents fir together as pieces of a jigsaw puzzle do
• Alfred Wegener theorized in the past that the continents were once joined as a single supercontinental he called Pangaea
• Wegener's theory would be later be improved upon, leading to a new theory - the theory of plate tectonics
• the theory of plate tectonics explains the formulation, the movement, and the changes of the outer, rigid layers of Earth
• one of the theories used to develop the plate tectonics theory is the seafloor spreading theory
• the seafloor spreading theory was theorized by American geologist Harry Hammond Hess
• according to the seafloor spreading theory, the seafloor splits and moves apart
• new oceanic crusts/floor is formed from the magma underneath the seafloors as it rises and fills the gap
• new oceanic crust forms continuously at the crust of the mid-ocean ridge.
• oceanic ridges are long, high, and continuous chains of mountains that seem to run around Earth
• the Mid-Atlantic Ridge is one such oceanic ridges that is located at the center of the Atlantic Ocean basin
• to test the theory, samples of volcanic rocks were taken from the ocean floor
• the age of the sample rocks was determined and found that the rocks near the mid-ocean ridge are younger than those farther from the ocean ridge
• petrologists study the origin, composition, distribution, and structure of rocks.
• a divergent boundary exists between two plates that move apart
• a convergent boundary lies between two tectonic plates moving towards each other