Earth's Systems

Cycle of Matter

Matter cycles through an ecosystem. In the water cycle, heat causes water to evaporate into the atmosphere. Water then cools and falls from the atmosphere as precipitation. Other forms of matter also have cycles that affect living things.

Fossil Fuels

Burning fossil fuels can release nitrogen oxide (NO2) into the atmosphere. Water washes excess nitrogen oxide into bodies of water, where it can deplete oxygen levels and hurt wildlife. Other chemicals released are hydrocarbons and sulfur oxides. Carbon dioxide leads to the greenhouse effect and global warming.


Earthquakes are seismic waves caused by the release of energy in the Earth’s crust. The scale used to measure the severity of earthquakes is called the Richter scale. Areas prone to earthquakes have special building practices.


Hurricanes, also called severe tropical cyclones, are low-pressure, spiral-shaped thunderstorms. They can cause severe rains, flooding, wind damage, high waves and storm surges. Building levees can mitigate damage from hurricanes.

Renewable Resources

Renewable energy sources will not be depleted. Wind, solar, geothermal (heat from deep underground) and biomass (burning plant material and animal waste) energy are all renewable.

Non-renewable Resources

Fossil fuels like coal, oil and gas are non-renewable resources because there is a finite amount of them in the Earth. They take a very long time to develop, and are being used at a faster rate. As non-renewable resources are depleted, they become more expensive and less practical to use for energy.


The ability for people to maintain their way of life is called sustainability. Using renewable resources is sustainable because they will not be used up.

Earth’s Atmosphere

Earth’s atmosphere is divided into five layers. The troposphere is the closest layer of the atmosphere, and where most weather takes place. The stratosphere is next and it is the highest level jets can reach and contains the ozone layer. The third layer is the mesosphere, which is the coldest place on Earth and too high for jets and too low for satellites. The thermosphere is the fourth layer and has very low air pressure and high temperatures with no water vapor. The fifth layer is the exosphere, which merges with space and is where most satellites orbit.

Gases in the Atmosphere

The Earth’s atmosphere is about 78% nitrogen and 20% oxygen, with the rest being a combination of many other gases.

Climate Change

Increased carbon dioxide in the atmosphere can trap more radiated heat from the Sun in the atmosphere. Global warming could cause changes in weather, food production and ocean levels.


Oceans are bodies of salt water that contain most of Earth’s water. Ocean currents are large movements of water in the ocean. Wildlife travel on ocean currents, and ocean currents are the reason the ocean may feel warmer or colder


Tides in the oceans are caused by the gravitational pull of the Moon. When the moon is over the ocean, its gravity pulls the water toward it, causing it to recede from the shore in a low tide.

Coral Reefs

Many organisms live in the oceans. One of the places with the greatest diversity of ocean life is a coral reef. Coral reefs are giant structures made of calcium secreted by corals, a type of underwater invertebrate. Coral reefs provide shelter for fish and other creatures.

Earth’s Interior

The interior of the Earth has four layers. The crust is the outer layer that we live on. It is the thinnest layer, but the only layer most people ever see. The mantle is the next layer; it is a thick layer of solid rock. The outer core is a layer of very hot liquid. The inner core is the very dense innermost layer.

Earthquakes and Volcanoes

The Earth’s crust is made up of plates called tectonic plates. Where the plates collide, mountains and rifts are formed. Earthquakes are caused by the energy released when two plates rub together, collide or move apart. Volcanoes are caused by plates moving apart or colliding causing the release of gas and molten material from the Earth’s core. The location of the edges of the plates is clear on maps of the locations of earthquakes

Major Landforms

Some of the major landforms on the Earth are mountains, the continental shelf and ocean basins. The continental shelf is the flat piece of and that makes up the continents and the shallow water that surrounds them. The ocean basin is the deep part that makes up most of the oceans.










Earthquake Photo:  Germanna Community College;  Windmill Photo:  Steve Fareham; Ocean Photo:  Tiago Fioreze; Reef Photo:  Richard Ling