Read the original article.Īerial photo captured during an overflight of the Northeast Rift Zone eruption of Mauna Loa volcano in Hawaii, U.S., Nov. This article is republished from The Conversation under a Creative Commons license. If the composition changes or activity increases, that’s a pretty clear indication that the volcano is changing. Other ways that volcanic activity is monitored includes chemical analysis of gases coming out through fumaroles – holes or cracks through which volcanic gases escape. This allowed scientists to warn the public. A few weeks before the eruption of Mauna Loa, scientists noticed that the tremors came from ever shallower depths, indicating that magma was rising and an eruption might be imminent. Any movement of magma below will cause tremors that are picked up by the seismometers. Volcanoes like Hawaii’s are monitored with a large network of seismographs. Any change in the tilt on a volcano slope indicates that the volcano is “breathing,” again because of magma moving below.Ī very important tool is watching for seismic activity. On volcanoes, any upward movement on the surface detected by GPS indicates that something is pushing from underneath.Įven more sensitive are tiltmeters, which are in essence the same as bubble levels that people use to hang pictures on a wall. It can detect minuscule movements of a few centimeters. The way scientists use GPS is different from that of everyday life. The perhaps simplest to understand is GPS. Volcanic activity is monitored with many different instruments. How do scientists know what is happening under the surface? Thermal imagery shows the Mauna Loa eruption, which began around 11:30 p.m. So, the magma is less prone to clog volcanic vents on its ascent, which would ultimately lead to more explosive volcanism. It has a different chemical composition and flows much more easily. Oceanic magma is very different from continental magma. In fact, it is the most isolated volcanic hot spot on Earth, far away from any plate boundary. Hawaii is in the middle of an oceanic plate. Why does Hawaii typically see less dramatic eruptions than other locations? Cracks in the Pacific Plate then channel the magma upward toward the magma chamber beneath the island of Hawaii. Instead, it has twists and turns, originally coming from the southeast, but then turning toward the west of Hawaii as the plume reaches into the shallower mantle. Seismic imaging by research teams I’m involved with has shown that Hawaii’s mantle plume comes from deep inside the mantle.īut the plume is not a straight pipe as some concept figures suggest. The origin of the magma may be more than 620 miles deep, and some scientists have suggested it could comes from a depth of 1,800 miles, where the mantle meets Earth’s core. If a large enough opening exists at the surface, and enough volcanic gases have collected in the magma chamber, the magma is forced to the surface in a volcanic eruption. Because the overlying pressure lessens as the rock ascends, it melts more and more, and eventually collects in the magma chamber. The ascending mantle rock is what makes a mantle plume. The partially molten rock becomes buoyant and ascends toward the surface. Mantle rock is solid at some places, while it starts to melt at other places. Instead, differences in the type of mantle rock make it melt at different temperatures. Scientists hypothesize that the mantle is not made of uniform rock. How does molten rock travel from deep in Earth’s mantle, and what exactly is a mantle plume? The same thing happens at Haleakala, on Maui, which last erupted about 250 years ago. Beneath Hawaii, magma can move upward through the cracks to feed different volcanoes on the surface. The crust and mantle that comprise the Pacific Plate cracks at different places as it moves northwestward. But volcanoes can also be in the middle of plates, as Hawaii’s volcanoes are in the Pacific Plate. Volcanoes typically occur where these plates either move away from each other or where one pushes beneath another. Robinson/USGSĮarth’s crust is made up of tectonic plates that are slowly moving, at about the same speed as a fingernail grows. An illustration suggests what Hawaii’s mantle plume might look like.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |