GED Science: Atmosphere, Oceans, and Earth's Interior Concepts
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Overview
This chapter covers Earth's major parts, the atmosphere, the oceans, and the solid Earth, and how they interact. Many questions ask you to read a table of measurements or explain a cause and effect.
The atmosphere is about 78% nitrogen and 21% oxygen. From the ground up, its layers are the troposphere (where weather happens), the stratosphere (which contains the ozone layer that absorbs much of the Sun's ultraviolet radiation), the mesosphere, and the thermosphere. Greenhouse gases such as carbon dioxide and water vapor trap heat near the surface; adding more of them warms the climate. Wind blows from high air pressure toward low air pressure.
The oceans hold salt water and move heat around the planet. Warm currents such as the Gulf Stream make nearby coasts milder. When water stays too warm, corals can bleach.
Inside Earth are the crust, mantle, outer core, and inner core. The crust is broken into tectonic plates, and most earthquakes and volcanoes happen near plate boundaries. Where plates move apart at mid-ocean ridges, new ocean crust forms. Weathering by wind, water, and ice breaks rock down over time.
Key concepts
Earth's layers
Crust (where we live), mantle, liquid outer core, solid inner core.
Memory tipCrust is thin, like the skin of an apple.
Atmosphere
About 78% nitrogen, 21% oxygen. Layers: troposphere, stratosphere, mesosphere, thermosphere.
Memory tipWeather happens in the troposphere.
Ozone layer
Ozone in the stratosphere absorbs much of the Sun's UV radiation.
Memory tipOzone = UV shield.
Greenhouse effect
Gases such as CO₂ and water vapor trap heat given off by Earth's surface.
Memory tipOzone is about UV; greenhouse gases are about trapped heat.
Plate tectonics
Earth's crust is broken into moving plates. Most earthquakes and volcanoes happen at plate boundaries.
Memory tipLook at plate edges for earthquakes and volcanoes.
Weathering
Physical weathering breaks rock without changing its minerals; chemical weathering changes the minerals.
Memory tipChemical weathering makes a new material; physical does not.
Often tested
- Ozone layer (UV protection) and the greenhouse effect (trapped heat) are different things.
- Average rate of change = change ÷ number of years.
- Plates moving apart make new crust; plates moving together can make trenches or mountains.
3 sample questions
Verified practice questions from this unit.
Question 1. Which layer of Earth do people live on?
- ① Inner core
- ② Mantle
- ③ Outer core
- ④ Crust
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Answer: ④ Crust
Key point: Earth's layers: crust, mantle, outer core, inner core
Earth has four main layers. The crust is the thin, rocky outer layer we live on. Below it are the mantle, the liquid outer core, and the solid inner core.
Wrong choices
- Inner core: The inner core is solid metal at the center of Earth.
- Mantle: The mantle lies below the crust. It is hot rock that slowly flows.
- Outer core: The outer core is liquid metal deep inside Earth.
Question 2. Which gas makes up most of Earth's atmosphere?
- ① Carbon dioxide
- ② Hydrogen
- ③ Oxygen
- ④ Nitrogen
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Answer: ④ Nitrogen
Key point: Air is about 78% nitrogen and 21% oxygen
Dry air is about 78% nitrogen and about 21% oxygen. The rest is mostly argon, with small amounts of carbon dioxide and other gases.
Wrong choices
- Carbon dioxide: Carbon dioxide is a very small part of the air, well under 1%.
- Hydrogen: Hydrogen gas is almost absent from the lower atmosphere.
- Oxygen: Oxygen is about 21% of the air, the second most common gas.
Question 3. How does the ozone layer high in the atmosphere protect living things?
- ① It blocks all sunlight from reaching the ground.
- ② It traps heat to keep Earth warm at night.
- ③ It absorbs much of the Sun's harmful ultraviolet radiation.
- ④ It makes rain fall on dry areas.
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Answer: ③ It absorbs much of the Sun's harmful ultraviolet radiation.
Key point: Ozone layer (stratosphere) absorbs UV radiation
The ozone layer is in the stratosphere. Ozone absorbs much of the Sun's ultraviolet (UV) radiation, which can damage skin, eyes, and living cells.
Wrong choices
- It blocks all sunlight from reaching the ground.: Visible sunlight passes through the ozone layer. Only much of the UV is absorbed.
- It traps heat to keep Earth warm at night.: Trapping heat is the greenhouse effect, mainly caused by gases such as water vapor and carbon dioxide.
- It makes rain fall on dry areas.: Rain forms from water vapor in clouds in the lower atmosphere.
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