![]() These transform faults make the mid-ocean ridge system look like a giant zipper on the seafloor (Figure 4.5.2). #DIVERGENT BOUNDARY DEFINITION SERIES#Although oceanic spreading ridges appear to be curved features on Earth’s surface, in fact the ridges are composed of a series of straight-line segments, offset at intervals by faults perpendicular to the ridge, called transform faults. Running down the middle of the mid-ocean ridge is a rift valley 25-50 km wide and 1 km deep. Because the new crust formed at the plate boundary is warmer than the surrounding crust, it has a lower density so it sits higher on the mantle, creating the mountain chain. The mid-ocean ridge system is a giant undersea mountain range, and is the largest geological feature on Earth at 65,000 km long and about 1000 km wide, it covers 23% of Earth’s surface (Figure 4.5.1). Most divergent boundaries are located along mid-ocean oceanic ridges (although some are on land). By funding expeditions to spreading centers in the Atlantic and the Pacific, NOAA Ocean Exploration is helping scientists to draw connections between volcanic, tectonic, hydrothermal, and biological systems in order to better understand the Earth’s remarkable, evolving geography.Modified from "Physical Geology" by Steven Earle*ĭivergent boundaries are spreading boundaries, where new oceanic crust is created to fill in the space as the plates move apart. #DIVERGENT BOUNDARY DEFINITION CRACK#Due to the fast spreading rates, there is no rift valley in the Pacific, just a smooth volcanic summit with a crack along the crest that is much smaller than the Atlantic rift valley.ĭespite being such a prominent feature on our planet, much of the mid-ocean ridge system remains a mystery. In contrast, the East Pacific Rise is spreading quickly, at rates of 6 to 16 centimeters (3 to 6 inches) per year. The Mid-Atlantic Ridge runs down the center of the Atlantic Ocean, slowly spreading at a rate of 2 to 5 centimeters (0.8 to 2 inches) per year and forming a rift valley that is about the depth and width of the Grand Canyon. Two well-studied mid-ocean ridges within the global system are the Mid-Atlantic Ridge and the East Pacific Rise. The speed of spreading affects the shape of a ridge – slower spreading rates result in steep, irregular topography while faster spreading rates produce much wider profiles and more gentle slopes. As the plates separate, molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt. Mid-ocean ridges occur along divergent plate boundaries, where new ocean floor is created as the Earth’s tectonic plates spread apart. The majority of the system is underwater, with an average water depth to the top of the ridge of 2,500 meters (8,200 feet). The massive mid-ocean ridge system is a continuous range of underwater volcanoes that wraps around the globe like seams on a baseball, stretching nearly 65,000 kilometers (40,390 miles). This system forms the longest and largest mountain range on Earth, winding its way between the continents. New ocean crust, shown in this map in red, forms along the divergent plate boundaries of the ridge system. The nearly continuous, global mid-ocean ridge system snakes across the Earth’s surface like the seams on a baseball.
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