Basalt is a common extrusive igneous rock, there are a large number of volcanic provinces across Southeast Australia that have been found to contain basaltic lava flows. It is likely that these flows have come from volcanic activity caused by mantle plumes from the mesosphere. A variety of dating methods have been used to date these basaltic rocks, which have been aged from the Jurassic era right up to the late Cenozoic.
1. Composition of Basalt
Basalt is a commonly occurring igneous rock. More specifically however, Basalt falls under the category of Mafic Rocks. Mafic rocks have a poor Silica content, approximately 50% (Charles, Diane, Lisa, 2010) and contain high concentrations of metal oxides. Basalt is a fine grained rock containing predominantly ferromagnesian minerals, followed by plagioclase feldspar. The colour of Basalt ranges from dark grey to black and is relatively featureless. See Fig 1.
2. The formation of Basalt
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.
3. Methods of dating Basalti...
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...(1976),Potassium-argon ages for some Australian Mesozoic igneous rocks, Geological Society of Australia,Vol23,pg 1-9
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The Australian Museum, Photograph viewed on 1st March 2014, http://australianmuseum.net.au/Uploads/Images/8287/volc_01_big.jpg The United States Geological Survey, Photograph viewed on 2nd of March 2014,
http://pubs.usgs.gov/gip/dynamic/graphics/hot_spot.gif
Marshak, S. (2009) Essentials of Geology, 3rd ed. New York: W.W. Norton & Company, ch. 11, p. 298-320.
Illinois State Geological Survey, 2005, Time Talks – The Geology of Starved Rock and Matthiessen State Parks
The third alluvial deposition consists of sand, silt and minor inter-bedded gravel, and again indicates Brimbank Park’s changing geology over time. (Geological map of Victoria, 1973). These deposits, as well as a nearby fault suggest volcanic activity 5-1.6 million years ago, which explains the olivine basalt (fig. 2) deposits which date back to to the Silurian and Tertiary period.
...e morphed it into the quartzite that is seen surrounding the butte (4). Rocks that undergo this process are called metamorphic rock, which is the same as the rock seen years ago by dinosaurs and other extinct creatures. The quartzite rocks were formerly seafloor sediment that was forced upwards, and then surrounded by lava basalt flows. Once erupted through fissures and floods through out most of the area, lava flow eventually created enough basalt to form a thickness of about 1.8 kilometers (1). All of this basalt flow eventually led to the covering of most mountains, leaving the buttes uncovered. The igneous lava flows and loess is reasons that the Palouse consists of such sprawling hills, and rich soil for farming (2). In result of the lava flows, the Precambrian rock Quartzite was formed. And lastly covered by the glacial loess, which were carried by the wind.
Tarbuck E., Lutgens F., Tasa D., 2014, An Introduction to Physical Geology, 5th Ed, Pearson Education, Upper Saddle River, New Jersey.
Shown in the picture above is volcanic extrusive igneous rock known as andesite. They were imported here to Laguna Beach to help minimize erosion (Merton Hill, p. 10-11). Extrusive Igneous rocks are formed on Earths surface due to lava quickly cooling or mixing with different materials such as ash or cinders from an eruption. There are two different types of extrusive igneous rocks; Plutonic and Volcanic. Andesite is known for being gray in color and being made up of very coarse grainy textures, which make it much harder to break down than sedimentary rocks. Unlike loose gravel and other sediments igneous rocks are known for being able to slow down seismic waves from earthquakes which cause less damage to surface structures.
Stone Mountain rises in sharp contrast to the surrounding flat, rolling landscape creating a geomorphic monadnock. Geologists appear to have consensus of the volcanic origins and underground formation of t...
While Kamiak butte is primarily made of quartzite, it is surrounded by a thick layer of basalt. Basalt is an intrusive igneous rock. The basalt at Kamiak Butte is 6 to 17 million years old.1 It is dense and dark in color- grays or black hues.2 Through research I learned that the basalt at Kamiak Butte was formed on a rift zone. Lava flowed from the rift zone into the area. In turn flattening out what were the preexisti...
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.
"NPS: Nature & Science» Geology Resources Division." Nature.nps.gov » Explore Nature. Web. 05 Dec. 2011. .
Magma is a hot liquid made of melted minerals. Minerals can form crystals when they are cool. Igneous rock can form underground, where the magma cools. slowly. Or, igneous rock can form above ground, where the magma cools.
There are two types of Igneous rocks. The first is intrusive, which is when the magma slowly cools beneath the earths surface. Because the magma is cooling slowly it allows the rocks end result to form crystal- like pigments. Examples of intrusive igneous rocks are Diorite, Gabbro, Granite, Pegmatite, and Periodotite. All of these rocks are course and grainy. The other type is an extrusive Igneous rock. This lava erupts onto the surface of the earth and cools rapidly also forming crystals, the lava cools so fast that at times it allows the rocks to form as clear-like glass. Examples of these rocks are Andesite, Basalt, Obsidian, Pumice, Rhyolite, Scoria,
mineral equilibria of metamorphic carbonate ejecta (2). Fluid inclusions ([CO.sub.2] and [H.sub.2]O-[CO.sub.2]) in clinopyroxenes from cumulate and nodules indicate a trapping pressure of 1.0 to 2.5 kbar at about 1200 [degrees]C, suggesting that these minerals crystallized at depths of 4 to 10 km (3). The differentiated magma fraction was about 30% of the total magma in the reservoir, and a volume of about 2 to 3 [km.sup.3] was
The interior structure of the earth is made up of crust, the mantle and core (inner core and outer core). Earthquakes occur on the crust. Crust forms the external layer of the earth surface. On the crust, the plate tectonics forces are in charge of causing the abrupt earth movements. Due to the existence of an immense temperature and concurrent pressure difference in the outer layer and inner layer of the earth, convection currents occur at the mantle. This energy results from overwhelming decomposition of radioactive substances contained by the rocks found at the interior of the earth. The developed convection currents lead to movement of lava; cold lava finds its way to the interior of the earth crust, while the molten lava which is generally hot, leaves the interior of the earth to the outside of the earth crust. These kinds of circulations occur at different locations of the earth surface and consequently results in segmentation of the earth due to movement in different directions.