Do tectonic plate movements occur and become faster? How are tectonic plates moving? What are the tectonic plates called? How thick are tectonic plates? What is the smallest tectonic plate? What are the 3 types of plates? Which one of the following is not minor plate? Is Nazca a minor plate? What minor plate is the smallest? What is the largest and smallest tectonic plate? Why is the Nazca plate getting smaller? Why is the Nazca plate a divergent boundary? Will the Nazca plate get bigger or smaller?
What countries are on the Nazca plate? Is the Nazca plate convergent? What happens when two tectonic plates meet? What geological event is most likely to occur at this plate boundary in the future South America?
What type of action can happen when two tectonic plates collide with each other? What happens when two plates rub against each other as they move in opposite directions? The rate of spreading along the Mid-Atlantic Ridge averages about 2. This rate may seem slow by human standards, but because this process has been going on for millions of years, it has resulted in plate movement of thousands of kilometers. Seafloor spreading over the past to million years has caused the Atlantic Ocean to grow from a tiny inlet of water between the continents of Europe, Africa, and the Americas into the vast ocean that exists today.
The volcanic country of Iceland, which straddles the Mid-Atlantic Ridge, offers scientists a natural laboratory for studying on land the processes also occurring along the submerged parts of a spreading ridge. Iceland is splitting along the spreading center between the North American and Eurasian Plates, as North America moves westward relative to Eurasia.
The map also shows Reykjavik, the capital of Iceland, the Thingvellir area, and the locations of some of Iceland's active volcanoes red triangles , including Krafla. The consequences of plate movement are easy to see around Krafla Volcano, in the northeastern part of Iceland. Here, existing ground cracks have widened and new ones appear every few months.
From to , numerous episodes of rifting surface cracking took place along the Krafla fissure zone. Some of these rifting events were accompanied by volcanic activity; the ground would gradually rise m before abruptly dropping, signalling an impending eruption. Between and , the displacements caused by rifting totalled about 7 m. When the continental crust stretches beyond its limits, tension cracks begin to appear on the Earth's surface.
Magma rises and squeezes through the widening cracks, sometimes to erupt and form volcanoes. The rising magma, whether or not it erupts, puts more pressure on the crust to produce additional fractures and, ultimately, the rift zone. East Africa may be the site of the Earth's next major ocean. Plate interactions in the region provide scientists an opportunity to study first hand how the Atlantic may have begun to form about million years ago. Geologists believe that, if spreading continues, the three plates that meet at the edge of the present-day African continent will separate completely, allowing the Indian Ocean to flood the area and making the easternmost corner of Africa the Horn of Africa a large island.
The size of the Earth has not changed significantly during the past million years, and very likely not since shortly after its formation 4. The Earth's unchanging size implies that the crust must be destroyed at about the same rate as it is being created, as Harry Hess surmised.
Such destruction recycling of crust takes place along convergent boundaries where plates are moving toward each other, and sometimes one plate sinks is subducted under another. The location where sinking of a plate occurs is called a subduction zone. The type of convergence -- called by some a very slow "collision" -- that takes place between plates depends on the kind of lithosphere involved. Convergence can occur between an oceanic and a largely continental plate, or between two largely oceanic plates, or between two largely continental plates.
If by magic we could pull a plug and drain the Pacific Ocean, we would see a most amazing sight -- a number of long narrow, curving trenches thousands of kilometers long and 8 to 10 km deep cutting into the ocean floor. Trenches are the deepest parts of the ocean floor and are created by subduction. Off the coast of South America along the Peru-Chile trench, the oceanic Nazca Plate is pushing into and being subducted under the continental part of the South American Plate.
In turn, the overriding South American Plate is being lifted up, creating the towering Andes mountains, the backbone of the continent. Strong, destructive earthquakes and the rapid uplift of mountain ranges are common in this region. Even though the Nazca Plate as a whole is sinking smoothly and continuously into the trench, the deepest part of the subducting plate breaks into smaller pieces that become locked in place for long periods of time before suddenly moving to generate large earthquakes.
Such earthquakes are often accompanied by uplift of the land by as much as a few meters. On 9 June , a magnitude This earthquake, within the subduction zone between the Nazca Plate and the South American Plate, was one of deepest and largest subduction earthquakes recorded in South America. Fortunately, even though this powerful earthquake was felt as far away as Minnesota and Toronto, Canada, it caused no major damage because of its great depth.
Magnitude is complicated, but it is important to understand that for large earthquakes, minor increases in magnitude result in huge jumps in released energy. With each whole number increase in magnitude, the energy release increases about 32 times. And with the increase of two whole numbers, the energy release increases about 1, times. For example, a magnitude 8. The December 26, , earthquake in the Indian Ocean had a magnitude of 9. Three months later, on March 28, , a magnitude 8.
Despite the small numerical difference in magnitude just 0. You may find it easier to understand another measurement of earthquake size, its intensity. Intensity is based on the observed effects of an earthquake's shaking e. This scale features increasing levels of intensity effects and ranges from not felt to total damage.
Unlike magnitude, intensity varies with location. Since intensity values are assigned after an earthquake, they do not support the real-time needs of tsunami warning centers. Earthquakes are not unusual. According to the U. Geological Survey, there are an estimated , detectable earthquakes in the world each year. Magnitude 2. On average, earthquakes greater than magnitude 7. The word tectonics comes from the Greek root 'to build.
Geological Survey. Please Contact Us. Toggle navigation JetStream. Layers of the earth. All plates Plate motion. Mariana trench Mid-Atlantic ridge Pacific-Antarctic ridge. Reverse fault Normal fault Strike-slip fault. Reverse fault. Normal fault. Strike-Slip fault. Earthquake located on a computer through an automated process based on information from seismic stations.
Animation comparing the relative sizes of some large historic earthquakes.
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