Earth and Space Science: GED Test Prep
Humans have always wondered about the origin of the Earth and the universe that surrounds it. What kinds of matter and energy are in the universe? How did the universe begin? How has the Earth evolved? This article will answer these fundamental questions and review the key concepts of Earth and space science.
Earth and space science are concerned with the formation of the Earth, the solar system and the universe, the history of Earth (its mountains, continents, and ocean floors), the weather and seasons on Earth, the energy in the Earth system, and the chemical cycles on Earth.
Energy in the Earth Systems
Energy and matter can't be created or destroyed. But energy can change form and can travel great distances.
The Sun's energy reaches our planet in the form of light radiation. Plants use this light to synthesize sugar molecules, which we consume when we eat the plants. We obtain energy from the sugar molecules and our bodies use it. Ultimately our energy comes from the Sun. The Sun also drives the Earth's geochemical cycles, which will be discussed in the next section.
The Sun heats the Earth's surface and drives convection within the atmosphere and oceans, producing winds and ocean currents. The winds cause waves on the surface of oceans and lakes. The wind transfers some of its energy to the water, through friction between the air molecules and the water molecules. Strong winds cause large waves. Tsunamis, or tidal waves, are different. They result from underwater earthquakes, volcanic eruptions, or landslides, not wind.
Energy from the Core
Another source of Earth's energy comes from Earth's core. We distinguish four main layers of Earth: the inner core, the outer core, the rocky mantle, and the crust. The inner core is a solid mass of iron with a temperature of about 7,000°F.Most likely, the high temperature is caused by radioactive decay of uranium and other radioactive elements. The inner core is approximately 1,500 miles in diameter. The outer core is a mass of molten iron that surrounds the solid inner core. Electrical currents generated from this area produce the Earth's magnetic field. The rocky mantle is composed of silicon, oxygen, magnesium, iron, aluminum, and calcium and is about 1,750 miles thick. This mantle accounts for most of the Earth's mass. When parts of this layer become hot enough, they turn to slow moving molten rock or magma. The Earth's crust is a layer from four to 25 miles thick consisting of sand and rock.
The upper mantle is rigid and is part of the lithosphere (together with the crust). The lower mantle flows slowly, at a rate of a few centimeters per year. The crust is divided into plates that drift slowly (only a few centimeters each year) on the less rigid mantle. Oceanic crust is thinner than continental crust.
This motion of the plates is caused by convection (heat) currents, which carry heat from the hot inner mantle to the cooler outer mantle. The motion results in earthquakes and volcanic eruptions. This process is called plate tectonics.
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