Conversations with the Earth Final Paper - How the Surfaces of Earth Are Formed and Changed

Conversations with the Earth Final Paper

How the surfaces of Earth are Formed and Changed

Earth is a rocky planet. Out of all the rocky planets, Earth is the largest and densest (1). The planet formed about 4.5 billion years ago. The Earth's interior is divided into four different layers, each having different characteristics and are each made of different elements and minerals (1). The Earth's surface is made up of 70 % water, and the other 30% is made up of the seven continents (2).

The surface is made of rock, this formed due to the cooling of lava at the surface about 4.5 billion years ago. The Earth's crust is broken up into many different plates, also known as tectonic plates. These plates move very slowly, creating different landscapes. This provides some evidence to us that unlike the other planets, the surface of Earth is in motion. These plates are the main reason as to why Earth has so many different surface types and structures. The continental crust of Earth is built up of low density material like igneous rock, granite and andesite (3).

The Earth has two different types of crust. The ocean floors are composed of a dark, dense volcanic rock known as basalt. The dry land of the continents is made up of mostly light silicate minerals and granite. The oceanic crust is around 5 miles thick while the continental crust is an outstanding 25 miles thick, but in some spots is thinner than that. Water fills in the low areas over the thin basalt crust to form the world's oceans (10).

The planetary surface of Earth takes new shape over different geological periods of time because of the plate tectonics and erosion. Other reasons why the surface of Earth changes over time can be attributed to: steady weathering from precipitation, thermal cycles, chemical cycles, glaciations, coastal erosion, the buildup of coral reefs, and large meteorite impacts (3). There are many different types of features on Earth's surface due to the complexity of our planet. The surface is different from other planets because we are the only planet that has such large abundances of water in one place (1). Mountain Ranges originally formed because of the collision of two plates, forcing the edges of the plates up (2). This is the same reason as to why structures like volcanoes and plateaus are formed the way they are.

Mountains are built by a plate sinking into the Earth's mantle and dragging on a small land mass or continent. . Continental crust is too thick and light to sink. Instead, it collides with the opposing plate. If the opposing plate is also a continent, neither plate will sink. This is the type of collision that usually forms a large mountain chain the middle of a continent. A perfect example of this is the Himalayas.

Orogeny is what the series of events is called during the formation of a mountain range. The elevation of mountains, volcanic activity, formation of plutonic and metamorphic rocks that occur when plates collide, and the folding and crumpling of rocks are all a part of orogeny.

The tectonic plates are the backbone of the Earth's surface. There are nine large plates and a number of smaller plates. While most plates are comprised of both continental and oceanic crust, the giant Pacific Plate is almost entirely oceanic, and the tiny Turkish-Aegean Plate is entirely land. Of the nine major plates, six are named for the continents embedded in them: the North American, South American, Eurasian, African, Indo-Australian, and Antarctic. The other three are oceanic plates: the Pacific, Nazca, and Cocos (5). Many people have compared the plates to puzzle pieces, they are large structures that all fit together to form Earth.

What keeps these plates moving are convection currents (4). Convection occurs because the density of a fluid is related to its temperature. Hot rocks lower in the mantle are less dense than their cooler counterparts above. The hot rock rises and the cooler rock sinks due to gravity (4). To the common person, the best way to prove that tectonic plates exist would be to look at the seven continents, they all seem like they would fit together to form a giant continent. The first person to propose this idea was a German Scientist named Alfred Wegener (4).

Volcanoes are openings in Earth's surface. There are three types: shield, cinder cone, and stratovolcano. A shield volcano has many layers of runny lava and flow piles up to form a mountain with gentle slopes. A cinder cone is Made up of many layers of broken rocks and ash. They wear away easily because there's no "glue" lava to hold it together. Finally A stratovolcano is made of alternating layers of ash and lava. The hardened lava is the "glue" that keeps the layers from wearing away quickly. These are often very large volcanoes (7).

The most major reminder that the United States has seen about how powerful these volcanoes can be occurred on May 18th 1980. The state of Washington was shocked when it learned that Mt. St. Helens erupted with the force comparable to that of a hydrogen bomb (5). The mountain had been dormant for 123 years. The explosion was so great that it blew off 1,300 feet of the mountains tops, and shot debris and ash 12 miles high. Sixty two people died, forests and lakes were diminished causing around $3 billion worth of damage (5).

What makes things like Mt. St. Helens occur are due to the plate boundaries. There are three different types of boundaries, Divergent boundaries, Convergent boundaries, and Transform boundaries. As the giant plates move, diverging or converging along their borders, tremendous energies are unleashed resulting in tremors that transform Earth's surface (5). A single plate cant move without affecting all of the others

Divergent Boundaries is where new crust is created, this happeneds because one plate pulls away from another. These boundaries are responsible