Earth Systems and Resources (Unit 4)

Asthenosphere

The soft, flexible upper layer of the mantle, on which the tectonic plates move

Continental Drift

The theory that all of Earth’s continents were once joined together into a single large landmass, and then moved apart, forming the continents we see today

Convection

Transfer of heat by movement of a fluid 

Convection currents

Movement within hot fluids, when the heat source is on the bottom, such as in a boiling pot of soup on the stove. Happens because the hotter material is less dense and rises; when it reaches the surface, it cools and becomes less dense, so it sinks. This rising and sinking creates a circular motion within the fluid. 

Convergent Plate Boundaries

Where two tectonic plates move toward each other 

Divergent Plate Boundaries

Where two tectonic plates move away from each other 

Gondwana

The southern continent formed when Pangaea split into two pieces 

Laurasia

The northern continent formed when Pangaea split into two pieces 

Lithosphere

The rigid, brittle layer made up of the crust and the uppermost part of the mantle. It is broken up into pieces called tectonic plates. 

Mantle Convection

Convection currents in the mantle that occur because hot rock in the lower part of the mantle is less dense and rises, and cooler rock in the upper part of the mantle cools, becomes more dense, and sinks. This is thought to be the mechanism driving the movement of tectonic plates. 

Mid-Ocean Ridge

A system of connected underwater mountain ranges that run throughout the world’s oceans. There is a rift valley in the center, where magma rises up from the mantle, and pushes out to either side, producing seafloor spreading. 

Pangaea (“All Land)

The single huge supercontinent that existed 245 million years ago, when all of Earth’s continents were joined together.

Seafloor Spreading

The process by which new oceanic crust forms when magma rises up and solidifies at the mid-ocean ridges. The newer crust pushes the older crust out to each side, which is why the age of the sea floor increases with distance away from the mid-ocean ridges. 

Subduction

The process by which one tectonic plate sinks below another, returning to the mantle, where the rock is re-melted. Takes place at convergent plate boundaries. Oceanic crust, which is denser, will always subduct under the less dense continental crust. 

Tectonic Plates

Large pieces of the lithosphere that slowly move on top of the asthenosphere. There are seven primary plates and many smaller ones. The seven primary plates are the African Plate, Antarctic Plate, Eurasian Plate, Indo-Australian Plate, North American Plate, Pacific Plate, and South American Plate. 

Tectonic Plate Boundary

A place where two tectonic plates meet 

Transform Plate Boundary

Where two tectonic plates slip past each other, moving in opposite directions

Atmosphere

The layer of air that surrounds the Earth (like a blanket).  Made up of a mixture of gaseous elements and compounds and a small amount of tiny solids and liquids. Is held close to Earth due to gravity. 

Thermosphere

The atmospheric layer between the mesosphere and the exosphere where the molecules contain the most heat energy; the Northern and Southern lights, known as the auroras are found here.

Ionosphere

The temperature increases as altitude increases

Mesosphere

The middle layer of Earth’s atmosphere where most meteoroids burn up. The temperature decreases as altitude increases. 

Jet Stream

“Rivers” of high-speed air in the atmosphere, found in the top section of troposphere/early stratosphere. It affects air masses and affects aircraft by speeding or slowing their path. 

Ozone Layer

A layer of a special kind of oxygen (O₃) found in the stratosphere that protects life on Earth from the sun’s harmful ultraviolet rays 

Stratosphere

The second layer from the Earth’s surface. It contains the ozone layer. The temperature increases as altitude increases due to the ozone layer’s absorption of ultraviolet rays from the sun.

Troposphere

The lowest layer of the atmospheric, containing about 75% of all the air in the atmosphere. It contains the air we breathe and is where weather, clouds, and air pollution are found. The temperature decreases as altitude decreases 

Air Pressure

The amount of force pushing on a surface or area.

Low Pressure

When air warms, its molecules scatter, the air becomes less dense and it rises. Air is usually cloudy and winds are particularly strong

High Pressure

When air cools, its molecules move closer together, the air becomes more dense and it sinks. Weather is fair and winds typically light. 

Radiation

The transfer of energy (including heat) through electromagnetic (light) waves. Examples include: radio, microwave, infrared, ultraviolet, visible light, x-rays, gamma rays 

Ultraviolet Rays (UV Radiation)

A form of energy given off by light with wavelengths that are shorter than visible light. Harmful to living things 

Wind

Horizontal movement of air from an area of high pressure to an area of lower pressure