It is the lasting remnant of an ancient ocean, the Tethys, that is shrinking as Africa and Europe collide in the Alpide orogeny. At million years, it still pales in comparison to the four-billion-year-old rock that can be found on the continental crust. The ocean floor is a mysterious place that marine geologists and oceanographers have struggled to fully grasp.
In fact, scientists have mapped more of the surface of the Moon, Mars, and Venus than the surface of our ocean. You may have heard this fact before, and while true, there is a logical explanation as to why.
Seafloor mapping, in its earliest, most primitive form, consisted of lowering weighted lines and measuring how far the sunk. This was done mostly to determine near-shore hazards for navigation. The development of sonar in the early 20th century allowed scientists to get a clearer picture of seafloor topography.
It didn't provide dates or chemical analyses of the ocean floor, but it did uncover long oceanic ridges, steep canyons and many other landforms that are indicators of plate tectonics. The seafloor was mapped by shipborne magnetometers in the s and produced puzzling results - sequential zones of normal and reverse magnetic polarity spreading out from the oceanic ridges. Later theories showed that this was due to the reversing nature of Earth's magnetic field. Every so often it has occurred over times over the past million years , the poles will suddenly switch.
As the magma and lava cool at seafloor spreading centers, whatever magnetic field is present get ingrained into the rock. The ocean plates spread and grow in opposite directions, so rocks that are equidistance from the center have the same magnetic polarity and age. For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher.
They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource. If a media asset is downloadable, a download button appears in the corner of the media viewer.
If no button appears, you cannot download or save the media. Text on this page is printable and can be used according to our Terms of Service.
Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. These tectonic plates rest upon the convecting mantle, which causes them to move. The movements of these plates can account for noticeable geologic events such as earthquakes, volcanic eruptions, and more subtle yet sublime events, like the building of mountains.
Teach your students about plate tectonics using these classroom resources. Ocean currents are the continuous, predictable, directional movement of seawater driven by gravity, wind Coriolis Effect , and water density. Ocean water moves in two directions: horizontally and vertically.
Horizontal movements are referred to as currents, while vertical changes are called upwellings or downwellings. Explore how ocean currents are interconnected with other systems with these resources.
In , after decades of tediously collecting and mapping ocean sonar data, scientists began to see a fairly accurate picture of the seafloor emerge. The Tharp-Heezen map illustrated the geological features that characterize the seafloor and became a crucial factor in the acceptance of the theories of plate tectonics and continental drift.
Today, these theories serve as the foundation upon which we understand the geologic processes that shape the Earth. The theory of plate tectonics revolutionized the earth sciences by explaining how the movement of geologic plates causes mountain building, volcanoes, and earthquakes.
Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Seafloor spreading is a geologic process in which tectonic plate s—large slabs of Earth's lithosphere —split apart from each other.
Seafloor spreading and other tectonic activity processes are the result of mantle convection. That's according to a study published in Nature, which helps answer a long standing question about what happens to tectonic An international team of scientists Print Email Share.
Most Popular Stories. It's in the Father's Genes. Living Well. Why is the seafloor so recent and the continental crust so old? Where do we find the oldest continental rocks and the oldest seafloor? What are the different types of rocks?
What is a fossil and what are they used for? What are hydrothermal vents, and why do we find them along mid-ocean ridges? Seismology What is a seismic wave? What is the difference between body waves and surface waves, and between P-waves and S-waves?
Why can't S-waves travel through liquids? How far can seismic waves reach? Why do P-waves travel faster than S-waves? Why is the interior of the Earth hot? What is the magnetic field of the Earth? Earthquakes and Faults Why do tectonic plates move? Brief history of the plate tectonics theory Before colliding with Asia, where was India? What is an earthquake? What is the highest magnitude an earthquake can reach?
0コメント