Week 4 GeoVids
Earth Revealed 13
This episode was about the volcanic process and how tectonic plate boundaries is related to that process. The video starts opened with the discovery of volcanoes on other planets in our solar system, like Venus. Volcano’s are partly responsible for providing atmospheres on planets. The video went on about how volcanoes give us clues about what is happening inside the Earth. Volcanoes are the product of the pressure buildup of molten magma that is being forced up because of the more dense surrounding rock. Most of the volcanoes on Earth are suspected to reside in the oceans, especially in the Mid Atlantic Ridge mountain range, which creates the oceanic crust. The video then talked about a hot spot volcano, which is a fixed place where magma comes out the the earth. As the crust moves over the hot spot, its former volcano becomes extinct and the hot spot creates a new volcano. A hot spot Shield volcano is a kind of volcano that is easily capable of spreading its lava flow for dozens of miles. Most volcanoes don’t have a crater, most are cracks in the crust called rift zones. Most land volcanoes are located on crust convergent zones, which is where the oceanic crusts and continental crust meet. These are called Composite volcanoes, which tend to be most explosive than Shield volcanoes. The video went about how magma bubbles rushes to the surface when a volcano forms, which is where holes and bubbles in some volcanic rocks come from. The video talked about the differences in the mineral and chemical make up between Shield and Composite volcanoes, Composite volcanoes contain more silicon than Shield volcanoes, which is why Composite volcanoes are most explosive. The video also talked about the different kinds of lava. The stereotypical volcano is called the Cinder cone volcano. The video went on about the relationship of volcanoes and ore deposits and clues that scientists use to predict volcanic eruptions.
Earth Revealed 14
This video was about how magma goes into crevices to from dams and dikes of “intrusive igneous rock” without ever being forced out onto the surface. The video also talked about how this process is related to plate tectonics. The geologist James Hutton came up with the idea that mountains and other geological formations were formed by volcanic magma that comes out of the Earth. The term to classify these kinds of rocks became known as Igneous rocks, which means “fire formed rocks”. The process of when magma ascends to the surface is called intrusion, so intrusive igneous rock means magma rose close to the surface, cooled, and continued to rise until is came out onto the surface to create geological formations. If the magma erupts before it cools underground, it is called volcanic rock. The video then talked about Mafic, Felsic, and intermediate rocks. Mafic rocks contain a lot of iron and magnesium, which is why they are dark colored. Felsic rocks contain a lot of silicon and aluminium, which is why they are light colored. Intermediate rocks contain both mafic and felsic rocks that can be seen without magnification. The video talked about how these rocks form, which has to do with when and where they cool off. The location of these rocks tell geologist the story of how they got to the surface, which helps us understand what the Earth’s interior looks like. The video went on about the formation and different types of magma. The video also talked the formations of crystals and some characteristics of rock fragments like xenoliths, batholiths, and how magma changes the chemical make up of rocks. In a nutshell, the crust and mantle is look a pressure cooker that creates different things at different levels.
Earth Revealed 15
This episode was about how atmospheric conditions is partly responsible for rock erosion and formation of soil. The video starts with the comparison of Egyptian hieroglyphs with one located in a pyramid and one location outside. The hieroglyph in the pyramid was more preserved than the hieroglyph outside because it wasn’t exposed to the weather. The video then talked about when rocks come out onto the surface, it goes through a process called exfoliation, which is the shedding of its surface. When the process of exfoliation happens, then the break down of the rock through the process called weathering becomes much easier. An example of weathering is when water gets in the cracks of rocks then expands when frozen, which then cracks the rock even more. There are different kinds of weathering mentioned in the video. The previous example was called chemical weathering. This process includes the acidification of rainwater and wind. Chemical weathering can also be called acidification. Plants may also be a kind of weathering. Another is called mechanical weathering, which is the process of the rock coming out the ground. The end result of all these methods of breaking down rocks is sedimentary rock or soil, which is what plants is essential for plant life, and therefore human life. I think that the process of weathering maybe the key thing in colonising Venus. Nature really is the ultimate teacher.
Earth Revealed 16
This episode was about mass wasting, which is the process of soil, sand, regolith, and rock moving downward as a mass. This process happens because the force of gravity. The video opens with a volcanic event in South America that caused a massive mudslide. This mudslide kill about 22,000 people. The two forces that cause mass wasting are “tectonic activity” and gravity. The “tectonic activity” portion has to do with volcanic activity building mountains and earthquakes and the gravity portion leads the “mass” downward. Mass wasting, or landslides, is an often occurrence in Washington state and is why engineering geologies are hired to find out if a selected site has the potential to become a landslide. They do this by drilling into the ground to find out what the ground is made of and how it is formed. Mass wasting happens because of the instability of a slope and the steepness of the slope. They also happen because of rain and water in the soil. Human activity usually doesn’t create the condition of a potential mass wasting, but can often trigger them to happen. Triggers including construction of roads, buildings and possibly dams. The video went on about the different kinds of mass wasting like slumps, creeps, rock slides, mudslides, debris flows, and landslides. A few years ago, I attended a court cases where a town was suing a company for causing a mudslide that hit their town. However, the verdict was the since 1500 mudslides happened in Washington in the same year this happened, it was unlikely the company caused it.
Earth Revealed 17
This episode was about exposed sedimentary rock layers and how they allow scientist to figure out the Earth’s geologic pass. Sedimentary dust is the end result of weathering and gets transported by wind and water. When sedimentary dust settles, it creates a bed, a rock layer formation that is separate from the layers above and below it. Sometimes when the dust settles on a angled landscape, it creates an angled layer called a cross-bed. Cross-beds are often associated with rivers and oceans, because of the rippling effect water. Over time, the layers compact and become cemented together from the weight over it, creating sedimentary rock. This process is called lithification. Sedimentary dust also comes together to form minerals. Most of the surface of land is made up of sedimentary rock. The video opens with the Grand Canyon and how because of its exposed layers, it is easy for geologists to decipher its history. A few of the things that geologists are able to tell from geologic history is if it was under water or if a lava flow came by. The video went on about where sedimentary dust in water can settle, like on the beach or river and ocean floors. Some of the things that geologists are able to decipher from cross-bed rocks is if it was exposed dry air because of how mud cracks. The decomposition of living things may also be in the geologic historical record, excluding fossils. If that is possible, then this would really help with determining the process of how oil is formed.
Earth Revealed 23
This episode was about how glaciers shape the landscape. Glaciers where believed to have been where they were for a million years, but in 1836 scientist Louis Agassiz discovered that the medieval inhabitants of Europe had repeatedly moved their towns away from the advancing glaciers. As glaciers retreat, the leave behind sediments that matches mountains hundreds of miles away, meaning that glaciers are a working to move and shape the landscape. The video then talked about how glaciers are made from the accumulation of snow in very cold climates over a long period of time, which is why glaciers are not found warm places like modern Australia. As snow piles on top of each other, it becomes more compact to for ice, which is a mineral. To find out how deep Glaciers where, scientist drilled holes with aluminium tubes until it hit rock. When they pull the tubes out a while later, the discovered the tube was bent, meaning that the time between the tube reaching the rock and them putting it out, the glacier had moved. Another piece of evidence that the glaciers moved was the polished rocks with glacial striations that were under them. Sometimes glaciers take much bigger rock samples with them, which is called tilling. Other ways to tell if a glacier existed, scientist look at a mountain side. Mountains with V shaped valleys didn’t have glaciers and mountains with a U shaped valley did. This is because of the ice carving into the sides as it slides slowly to the ground, making a smooth look. This process is called Basal sliding. The video went on about the different kinds of glaciers like continental and valley glaciers. The video also when on about why Ice Ages happen, thought the process is still not fully understood. And then the video talked about why the greenhouse effect is causing glaciers to melt at a fast rate.