The Mysterious Mountains Underneath the Sea: The Wonders of New England Seamounts Introduction Seamounts are one of the most pervasive landforms in the world, and can be seen in various frequencies throughout ocean basins. Seamounts are remnants of volcanoes and can be described as underwater mountains that can take various shapes and sizes. Islands and seamounts are similar in the way they are formed but they are different because seamounts do not reach the oceans surface. The pacific basin—mainly the pacific tectonic plate—contains half the seamounts that can be seen in satellite altimetry datasets. The other half of the seamounts that can also been seen by satellite altimetry datasets reside in the Atlantic and Indian oceans. Seamounts have steep flanks due to the cooling effect of the seawater as the magma pours out—unlike when the volcano is above sea level, the flanks are usually less steep. In deep waters the high water pressure allows a non-explosive eruption, taking the form of lava or pillow basalts. At this stage the seamounts remain circular. If the seamount is allowed to grow taller—and sufficient magma is available—then the flanks will express the gravitational stress by the development of rift zones, breaking the circular symmetry. As the seamount grows taller and reaches sea level, water pressure can’t contain the gases in the magma, as it can in deep water. When pressures can no loner suppress the volcanic reaction, it results in a higher rate of explosive eruptions. Once the island is established the volcano enters the shield building stage, building the island higher. However, once the volcano is inactive there is nothing to replace the erosion. The seamount is then brought back to sea level ... ... middle of paper ... ... as the oceanic plate moved over a hotspot as a rate of 4.7cm a year. The whole chain of New England seamounts took 20 million years to complete, and started about 100-103million years ago. Shape and size of seamounts varies—smaller seamounts are typically more symmetrically round where larger ones are asymmetrical due to rift zones. Seamounts affect local and global currents. As a current approaches a seamount upwelling occurs, mixing nutrient rich sediment into the waters. Some corals and sponges are known to have medicinal properties such as compounds for cancer treatment. Other studies show the benefit of using coral for bone grafting. Little is known about seamounts and the biodiversity that can be associated with them. From what we do know, seamounts are important features of the ocean, providing us with a whole diversity of life we have yet to explore.
Mauna Loa is located on a hot spot in the Pacific Ocean. It is not near a plate boundary, in fact it is 3,200 km from the nearest plate boundary, and is situated in the middle of the Pacific tectonic plate. This is actually a rarity, as 90% of volcanoes are along a tectonic plate boundary. A hot spot occurs where long, stationary vertical pools of magma rise up and towards the plate. Movement of the tectonic plates above the hot spot created Mauna Loa, along with the other Hawaiian volcanoes. The older Hawaiian Islands were once above this stationary hot spot, but have been carried northwest by the slowly moving Pacific plate. As the plate moves, it carries the previously formed, older, volcanoes with it, creating a trail of younger, new volcanoes behind. The islands are lined up along the Hawaiian Ridge-Emperor Seamounts chain, which is 3,750 miles and includes Kauai, Maui, Oahu and Hawai’i, from north to south, respectively. There are around 80 volcanoes in this chain; most of them underwater, consequently the term seamount refer to submarine volcanoes. Three volcanoes of Hawai’i, Mauna Loa, Kilauea and Loihi seamount, are all currently sharing the Hawaiian hot spot. Although, recent evidence has shown that all three volcanoes use have separate plumbing systems to expel the lava from the pool of magma deep below them. It has also been suggested that Loihi is slowly moving Mauna Loa from the center of the island, thus shifting directly over the hot spot. The closer to the hot spot a volcano is, the more active it will be. The Hawaiian hot spot has laid down layers of lava, building up enormous islands from the ocean floor.
Over the centuries, the making of the Big Island as we know it today eventually entailed the growth and conjoining of six separate volcanoes, building all the way up from the seafloor, some 18,000 feet below the ocean’s surface. These volcanoes, from northwest to southeast, are named Mahukona, Kohala, Mauna Kea, Hualalai, Mauna Loa and Kilauea, and become younger as one moves north to south. Mahukona Volcano, just off the Big Island’s northwest coast, was the first volcano to start forming. Now submerged beneath the surface of the ocean because it is sinking into the Earth’s crust under its own vast weight, Mahukona is no longer visible. As the Pacific Plate slowly continued moving northwestward over the hotspot, the location of the rising magma moved relatively southeastward, and through time the rest of the Big Island volcanoes formed along that path.After Mahukona, Kohala Volcano, the precursor to today’s Kohala Mountain, erupted next. As Kohala Volcano emerged from the sea and joined with Mahukona, a much larger Big
Basalt forms due to the partial melting of the layer of the mantle called the asthenosphere. The asthenosphere is the plastic zone of the mantle beneath the rigid lithosphere. Mantle plumes coming from the mesosphere can cause the asthenosphere to melt with heat or even if pressure decreases, which is called decompression melting (Richard 2011). The magma that forms from this melting is mafic magma that solidifies once it reaches the earth’s surface and cools quickly. The above process mainly occurs mainly during intraplate igneous activity which is the main explanation for volcanic activity that occurs a long distance away from a plate boundary. If the tectonic plate above the mantle plume is moving it can create a string of volcanic activity such as in Hawaii. See Fig 2.
When the plates mash together on a convergent boundary, they can create an earthquake. A place with a convergent boundary is New Zealand. When the plates pull apart, a divergent boundary, they create a hole in the ocean that causes molten lava to rush up and it causes a volcano to form. A place with a divergent boundary is Iceland. With about 130 volcanoes all together, it has the most volcanoes of any country in the world and is on two tectonic plates. Santorini is currently in an area of earth where the African and Eurasian plate meet, and Atlantis disappeared with a rumble that could have come from a volcano or an
Four tectonic environments in which magmatism occurs: destructive plate margins, constructive plate margins/divergent plate boundaries, oceanic intraplate and continental intraplate. Arcs are magmatic products of destructive plate margins (stern, 2001) which are referred to as sites where new continental crust is created and old oceanic crust is subducted back into the mantle (Hawkesworth , Hergt, McDermott, Ellam, 1991). An island arc is a form of an arc produced by the subduction of an oceanic plate beneath another oceanic plate (Hu, 2013). Island arcs are characterised by high large ion lithophile elements and low high field strength elements ((Hawkesworth , Hergt, McDermott, Ellam, 1991). New oceanic crust is created at the mid ocean ridges and by mass balance is then destroyed (recycled back into the mantle) at the subduction zones (Jarred, 2003). As it forms it undergoes hydrothermal alteration where the composition is changed from olivine, plagioclase and glass dominated to being dominated by clay minerals i.e. low grade metamorphism (green schist facies) (Jarred, 2003) where it becomes enriched in water, carbon dioxide and incompatible trace elements such as uranium and potassium. As the crust moves away from the ridge it accumulates sediments and becomes colder, older and dense enough to subduct. As the cold slab subducts into the hot mantle, it heats up. The slab goes to greater depths faster than it’s heated therefore pressure increases therefore hydrous minerals start to break down (Aizawa, Tatsumi, Yamada, 1999). The slab undergoes metamorphic reactions from hydrous green schist facies to amphibolite facies and finally to anhydrous eclogite facies at depths of less than 100 km (Ringwood, 1977). ...
... used to be a sea (Beaumont,1978). As mountain-building forces continued for several million years it created a big fold or anticline as it squeezed the rocks. These same pressures continued and overturned the fold which eventually caused them to break along a great low-angle fault (Beaumont,1978). The western limb of the fold was driven upward and eastern placing older layers of rock on top of younger ones. The younger layers of rock include cretaceous shales and sandstones. The slice of crust has been moved more than 15 miles toward the east, the surface it moved through is called the Lewis Overthrust. (Dyson,1957). Years of erosion finally exposed the fault which was buried throughout its early years. Erosion then separated several remnants, Chief Mountain is the best known which consists of Altyn limestone, exposed on its base is the Lewis Overthrust fault.
Volcanoes vary in shape, size, and type. Likewise, volcanoes have varied eruption styles, from beautiful fiery displays of explosive lava to pyroclastic flows of hot gases and ash. A volcano is an opening in the Earth’s surface where magma has erupted or poured through, generally resulting in hills or mountains (Abbott, 2014). This natural phenomenon has spawned a field of science known as volcanology. Volcanology is a branch of geological science that studies volcanoes, lava, and magma (RedOrbit.com, 2015). By studying volcanoes, volcanologists gain a better understanding of how volcanoes form and erupt.
In conclusion, Axial Seamount is an underwater volcano on the Juan de Fuca ridge, between the Juan de Fuca and the Pacific tectonic plates. It is one of the most active in the Northeastern Pacific region to this day. It has even been in the news on several occasions. Axial Seamount is fantastic example of how a mid-ocean ridge operates on a diverging plate boundary. However, we must remind ourselves that this is just one of the many interesting and unique volcano type on our home planet we call
Volcanism is a major part of the Galapagos and their formation. The island chain is positioned on the Nazca Plate, which is subducting beneath the South American Plate at a geologically rapid pace of 2.5 inches per year. In addition, this Nazca Plate is located directly on top of the Galapagos Hotspot. It is here that mantle plumes melt Earth’s crust, creating volcanoes as a product. The oldest island was first shaped by this ...
Stories about volcanoes are captivating. Myths come in different versions, but all of them are capable of capturing yours, and everybody’s imagination.
Volcanoes can be one of the most destructive forces on Earth. It is estimated that some
First you might need to know definition of tectonics. It is a theory in geology. The lithosphere of the Earth is divided into a small number of plates which float on and travel independently over the mantle and much of the Earth’s seismic activity occurs at the boundaries of these plates. That is the official definition of Plate tectonics. secondly, this plate covers many parts of continents. plate boundaries don’t go according to Continents boundaries, they make their own boundaries. The North American plat...
A volcano is landform (generally a mountain) where, during an eruption, ash, gas and molten rock (magma) escape through the Earths surface
The concurrent convective circulations in the mantle leads to some segments of the mantle moving on top of the outer core which is very hot and molten in nature. This kind of movement in different segments occurs as tectonic plates. These tectonic plates are basically seven on the earth surface as major ones, although, several small ones exist also. The plates motions are characterized by varying velocities, this variance results to sub sequential collision of two plates (leading to formation of a mountain in a convergent boundary), drift of two plates (leading to formation of rifts in a divergent boundary), or parallel movement in a transform boundary(Webcache 3).