Earth Science 2nd Sem Midterm

• There are three types of systems:

  Isolated, Closed, and Open system
• An isolated system is a system that does not allow matter and energy to leave or enter.
• A closed system is a system that allows energy to enter and leave but does not allow matter to leave
• An open system is a system that allows both energy and matter to enter and leave
• The Earth is essentially a closed system where there is only an exchange of heat and energy but no exchange of matter.
• Heat and energy are transferred between the Sun and Earth, and within the Earth, it is transferred between subsystems.
• Materials on Earth cycle between the four (4) subsystems: the Geosphere (land), Atmosphere (air),Hydrosphere (water),and Biosphere (living organisms).
• In contrast, the subsystems of the earth are open systems because matter and energy can flow across the boundaries between subsystems.
• The Geosphere contains all the rocks, minerals, and ground found on and in Earth. It includes the cold, hard solid land on the surface of the Earth (crust),the semi-solid land underneath the Earth (mantle), and the hot, liquid land in the center of the Earth (core).
• Crust is the thinnest layer of the Earth and is further divided into 2: continental and oceanic crust
• The continental crust is the thick layer of the crust that sits beneath the continents and is mainly made up of granite rocks
• The oceanic crust extends 5 to 10 kilometers beneath the ocean floors and is mainly made up of volcanic rocks called basalt
• The mantle is the thickest layer of the Earth (2,900 km thick) and comprises hot, dense rocks. There is a great difference in temperature between the lower and upper mantle.

  Because of this, the plates "float" on it like how oil floats on water.
• [Mantle]

  This "float" is described as convection currents that happen in the asthenosphere. The asthenosphere is the dense, weak layer of the mantle located below the crust that flows and moves the plates of the Earth. The very hot material causes convection currents at the deepest part of the mantle, rising, cooling, sinking, heating, rinsing, and repeating the cycle. When the convection currents flow in the mantle, they also move the plates of the Earth.
• The core is the hottest layer located at the center of the Earth. Unlike the crust and mantle, which are made up of rocks, the core consists of solid and molten metals. The core is further divided into 2 layers:
• Outer Core- The outer core is so hot (between 4,500o and 5,500°C) that the metals are all liquid. It is made up of melted metals nickel and iron.
• The pressure and temperature in the inner core are so great that the metals are squeezed together, preventing them from behaving like liquids. The metals are forced to vibrate in place as solid,which is why the inner core is a solid sphere composed mostly of iron metal.
• All those layers are separated from each other through a transition zone. These transition zones are called discontinuities.
• Conrad Discontinuity - A transition zone between the upper and lower part of the lithosphere.The name came from the Austrian geophysicist Vector Conrad. Up to the middle 20th century,the lower one consisted of more magnesium-rich rocks such as basalt
• Mohorovicic Discontinuity - The transition zone between the crust and mantle. The Mohorovicic discontinuity was discovered by Andrija Mohorovicic in the year of 1909. The Moho lies at a depth of 35km beneath the continents and 8km beneath the oceanic crust.
• Gutenberg Discontinuity - The mantle-core zone. In the year of 1912, Weichert Gutenberg discovered this discontinuity at a depth of 2900km beneath the earth's surface. It is a narrow, uneven zone and contains undulations that may be up to 5-8km wide.
• Repiti Discontinuity - The transition zone between the outer mantle and the inner mantle.
• Lehmann Discontinuity - It is the transition zone between the outer and inner core. It appears beneath continents and does not readily appear in globally average studies. Several Explanations have been proposed: (1) a lower limit to the pliable asthenosphere, (2) a phase transition, and (3) the most plausible, depth variation in the sea wave аnіsоtrору
• About 200 million years ago, it is believed that the continents were joined together in a huge landmass called Pangaea, as proposed by Alfred Wegener.
• The large-scale movement of Earth's plate is explained by the plate tectonic theory. Plate tectonic theory proposes that the lithosphere is divided into major plates resting upon the lower soft layer called the asthenosphere.
• The mechanism of movement of the plates is related to the convection current within the mantle. The lithosphere is also driven by processes such as erosion, weathering, and transport, as well as tectonic forces and volcanic activity, which results in the formation of landforms such as mountains, hills, and plateaus.
• Pangea's existence was first proposed in 1912 by German meteorologist Alfred Wegener as a part of his theory of continental drift. Its name is derived from the Greek Pangaea, meaning"all the Earth."
• The Atmosphere is a gaseous envelope held by gravity that surrounds the Earth. Without the Atmosphere, the Earth would be like a bigger version of the moon - cold and lifeless. The Atmosphere of the Earth is composed of 78% nitrogen (N), 21% oxygen (O), 0.9% argon (Ar), and a trace amount of gases known as Greenhouse gases such as hydrogen (0.00005%), helium (0.0005%), carbon dioxide (0.038%) and others.
• The Atmosphere comprises five layers-troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
• Troposphere - It is the lowest layer of the Atmosphere and extends up to 12km from the Earth's surface. It contains about 75% of the total mass of the Atmosphere and almost all of the water vapor. Weather phenomena and cloud formation occur in this layer. As altitude increases, temperature decreases because, at higher altitudes, the Atmosphere becomes thinner and absorbs less solar radiation.
• Stratosphere - The stratosphere extends from the top of the troposphere to about 50 km above the Earth's surface. In this layer, as altitude increases, the temperature also increases because of the absorption of ultraviolet (UV) radiation from the Sun by the ozone (03) in the ozone layer. The ozone layer protects us from the harmful radiation of the Sum. Still due to the increasing number of chlorofluorocarbons (CFCs) in the Atmosphere brought by human activities, the ozone layer is slowly depleting, making us vulnerable to the harmful radiation from the Sun. 6
• The mesosphere extends from the top of the stratosphere to about 80 km above the Earth's surface. This layer protects the Earth from meteoroids. Most meteoroids that enter the Earth's Atmosphere burn up due to intense friction between the air and the meteoroids. When meteoroids burn up in the Atmosphere, it is seen as a "shooting star" because of the streak of light caused by the hot, glowing gas from the burning meteoroid