Earth's estructure

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Earth's estructure by Mind Map: Earth's estructure

1. 4.2 Earth’s Crust Dynamics

1.1. Erosion or degradation

1.1.1. Eolic Caused by winds and dry climates

1.1.2. Pluvial: produced by rainfall and the water’s runoff.

1.1.3. Glacial: Caused by ice action.

1.1.4. Karst erosion: caused by the infiltration of surface water to underground water currents.

1.1.5. Marine: caused by waves, tides, and oceanic currents.

1.1.6. Anthropic: caused by human activities.

1.1.7. Biologic: Caused by plants and animals.

1.2. External forces

1.2.1. The weathering is the exposition of objects (rocks and soils) to the action of external agents such as light, heat, wind, rain, etc. (Sampieri, 2006). Physical weathering: It consists of the disintegration of rocks because of the heating and cooling that take place. Chemical weathering: It leads to the chemical decay of rocks because of oxidation, dissolution, hydration, and carbonation processes.

1.3. Volcanism and seismicity

1.3.1. Seismicity An earthquake is the result of the collision between two tectonic plates, their displacement or rearrangement. These movements release energy in the form of seismic waves. The point where the earthquake originates is called the hypocenter or focus, and the point directly above the hypocenter and over the Earth’s crust is called the epicenter. Volcanism is a consequence of the multiple movements of the tectonic plates. Collisions between plates create cracks through which magma and other solid and liquid elements are expelled to the Earth’s surface.

1.3.2. Volcanism

1.4. Landscape forms

1.4.1. Mountains Mountains are the highest elevations of the crust and can be originated by folding, that is if the rocks do not break, but fold when two plates collide. This happened, for example, in the formation of the Rocky Mountains in North America.

1.4.2. Plateaus

1.4.3. These formations are high plains or tablelands, which are areas of highland with relatively flat terrain. They are above 500 m above the mean sea level, like the Meridional Upland or the Anahuac Plateau.

1.4.4. Plains

1.4.5. Plains are, as their name suggests, even zones whose altitude does not exceeds 500 m above the mean sea level, like the Pampas in Argentina.

1.5. Tectonic Plates Theory

1.5.1. Starting from 1970, research done in the seabed led to the global tectonic theory.This theory is the framework to explain different process and geological phenomena, allowing us to deeply understand the Earth’s internal structure. That is the reason why it is a milestone for geology and, without a doubt, the most transcendental finding for this discipline during the twentieth century.

2. topic 4.1 earth's structure

2.1. crust

2.1.1. Oceanic crust: Basaltic rocks predominate. The oceanic crust covers the upper mantle and is the seat of the continental cortex.

2.1.2. These zones are separated from each other by the Conrad discontinuity, the nearest discontinuity to the Earth’s surface.

2.1.3. Continental crust: Its thickness has barely 35 kilometers, but it is greater in the mountainous zones. Granitic rocks predominate (rich in aluminum silicates).

2.2. litosphere

2.2.1. It is Earth’s outermost layer and is formed by the crust and the upper mantle. It is formed also by 16 tectonic plates that move above one of the mantle’s most fluent zone, called asthenosphere. It supports the lithosphere, including the continents. Here is where the volcanic eruptions and earthquakes happen.

2.3. Mantle

2.3.1. Lower mantle Also called interior mantle, is mainly composed of iron silicates and is solid.

2.3.2. Both mantles are separated from each other by the Repetti discontinuity.

2.3.3. upper mantle Also called exterior mantle, it is located just below the Earth’s crust. It contains magma. When it melts,it is expelled to the Earth’s through volcanic eruptions, cracks or fissures, as lava.

2.4. Nucleus

2.4.1. internal nucleus

2.4.2. Between both nuclei there is a zone called the Weichert-Lehman discontinuity. Despite its very high temperature (around 5000°C), it is solid because of the great pressures that the superior layers exert on it. It is composed mainly of nickel and iron.

2.4.3. External nucleus It is liquid and presents ascendant and descendant convective movements, what in turn is the basis of the Earth’s magnetic field.

3. 4.3 Geological Eras

3.1. Precrambrian

3.1.1. It started approximately 4 billion years ago, when the Earth’s crust started to solidify because of the rain’s action on the hot rocks, and ended 570 million years ago.The ocean was the habitat of the first unicellular organisms and of the first oxygen-producing organisms.

3.2. Paleozoic

3.2.1. The continents Laurasia and gandwana collide with one another to form a supercontinent called Pangea. The first vertebrates appeared.

3.3. Mesozoic

3.3.1. At this era, North America and Eurasia were created. Gondwana remained together until the end of this era; Dinosaurs reigned during this era, although birds and primitive mammals also appeared

3.4. Cenozoic

3.4.1. Collisions among plates give rise to mountain ranges in Asia, Europe and South America, i.e. the Himalayas, the Alps and the Andes respectively. Additionally, the Pacific Plate subduction causes the rise of the Oriental and Occidental Sierra Madre. The continents have the present conformation. This era is dominated by mammals, among them the primates.

3.5. Quaternary

3.5.1. There are evidences of a great glacial era started at the beginning of the Quaternary period, the most recent of the Cenozoic. the homo sapiens has been dominating the Quaternary.