RelativeDating. Education.nationalgeographic. Sediment is solid material that is moved and deposited in a new location. Sediment can consist of rocks and minerals, as well as the remains of plants and animals. It can be as small as a grain of sand or as large as a boulder. Sediment moves from one place to another through the process of erosion. Erosion is the removal and transportation of rock or soil. Water can wash sediment, such as gravel or pebbles, down from a creek, into a river, and eventually to that river's delta.
Glaciers can freeze sediment and then deposit it elsewhere as the ice carves its way through the landscape or melts. Wind can move dirt across a plain in dust storms or sandstorms. Sediment is important because it often enriches the soil with nutrients. For thousands of years, the Nile River flooded yearly and brought with it 4 million metric tons (4.4 million short tons) of nutrient-rich sediment. Sedimentary Rock Over millions of years, layers of sediment may build up and harden into sedimentary rock. Multimedia Discovery Missions | Lesson 2 - Mid-Ocean Ridges | Seafloor Spreading Activity. Seafloor Spreading Activity Most basalt magmas contain abundant molten iron. As magma starts to harden into rock, iron-rich minerals solidify first. Their crystals are pulled into alignment by the Earth’s magnetic field, just like a compass needle is pulled towards magnetic north.
Once the basalt cools completely into solid rock, the alignment of the iron minerals is fixed. Thus, basalts preserve a permanent record of the strength and direction, or polarity, of the planet’s magnetic field at the time the rocks were formed. When geologists studied the polarity of ancient rocks, they were stunned to discover that in many of them, iron minerals were aligned toward the south magnetic pole, not the north. In the 1970's, scientists sailed back and forth across the world’s oceans, measuring the magnetic signatures emanating from the oceanic crust beneath their ships. The figure below includes two images of the ocean floor. Questions Additional Information Critical Thinking [Possible Answer] Educational Materials | UK College of Arts & Sciences.
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