Shaping the Planets: Volcanism

What is volcanism?Volcanism is the eruption the molten absent (magma) onto the surface of a planet. A volcano is the vent v which magma and gases room discharged. Magma that reaches the surface is called “lava.” Volcanos are named for Vulcan — the roman god of fire!

Why and where execute volcanos form? Volcanism is the result of a planet losing its internal heat. Volcanos can form where rock close to the surface ar becomes hot sufficient to melt. On Earth, this often happens in association v plate borders (check out the section on tectonism). Where 2 plates move apart, such as at mid-ocean volcano ridges, product from Earth"s interior gradually rises up, melts once it reaches lower pressures, and also fills in the gap. Where one key is gift subducted under another, chambers the magma might form. This magma bodies feed the volcanic archipelago that mark subduction zones.

Although most volcanic task takes location at key boundaries, volcanism likewise can happen within the key interiors in ~ hotspots. Hotspots space thought to it is in from large “plumes” of incredibly hot material rising native deep in Earth"s interior. The hot material rises slowly, eventually melting as it reaches reduced pressures close to Earth"s surface. Once the material erupts it forms enormous lava operation of fine-grained dark volcanic rock — basalt. The broad, gentle shield volcanos the Hawai"i come indigenous a hotspot.

What perform Earth"s volcanos call us? The fact that planet has volcanos tells united state that Earth"s interior is circulating and is hot — hot sufficient to melt. Planet is cooling; volcanos space one method to lose heat. The pattern of circulation of volcanos on earth gives us a clue the Earth"s outer surface is divided into plates; the chain of volcanos connected with mid-ocean ridges and subduction zones note the bowl edges. Other planets have actually volcanic features — some newly active — informing geologists the they, too, room losing warmth from your interiors and that over there is circulation. However, this planets carry out not display screen the pattern that Earth"s volcanos do.

What proof is there of volcanism on various other planets? Moon: ours closest neighbor has little volcanos, fissures (breaks in the crust), and also extensive flows of basalt, a fine-grained dark volcanic rock. The large dark containers that you have the right to see top top the Moon are the maria — areas of these lava flows. However, every these volcanic features are old. There are no energetic volcanic features on the Moon. Most of the volcanic task took place early in the Moon"s history, before around 3 billion years ago. The many recent lava circulation occurred around 1 billion years ago.

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Mars: Mars has volcanic attributes that are comparable in form to those ~ above Earth, although much larger. Over there are large shield volcanos — like those in Hawai"i — that contain 100 times more mass that those ~ above Earth. Olympus Mons is the tallest volcano in our solar system. It is 22 kilometers (14 miles) tall, compared to Mauna Loa"s 9 kilometers (almost 6 miles). It is 600 kilometers across (375 miles), which is huge enough come cover the state of Arizona! number of of the volcanos top top Mars, including Olympus Mons, take place in the Tharsis region; the magma because that the volcanos might come from hot material welling up in plumes from deep in Mars" interior. Many scientists consider Mars to it is in volcanically active, even if we have actually not it was observed an eruption. Basalt meteorites indigenous Mars show that volcanism has occurred in the critical 180 million years.

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Very couple of impact craters happen on the lava operation of Olympus Mons, saying that this volcano has actually probably erupted in the last couple of million years.