Free GED Science Earth and Space Science Practice Test — Questions and Answers

Question 1: Which layer of the Earth is the thinnest?

Inner core
Outer core
Mantle
Crust (Correct answer)

Correct answer: Crust

Earth's crust is the outermost and thinnest layer — ranging from about 5 km under oceans to 35-70 km under continents.

Question 2: What is the primary gas in Earth's atmosphere?

Oxygen
Carbon dioxide
Nitrogen (Correct answer)
Argon

Correct answer: Nitrogen

Earth's atmosphere is approximately 78% nitrogen, 21% oxygen, and smaller amounts of other gases.

Question 3: Which type of rock forms when molten rock cools and solidifies?

Sedimentary
Metamorphic
Igneous (Correct answer)
Organic

Correct answer: Igneous

Igneous rock forms from the cooling and solidification of magma (underground) or lava (on the surface).

Question 4: What causes the seasons on Earth?

Earth's distance from the Sun varies throughout the year
The tilt of Earth's axis as it orbits the Sun (Correct answer)
The rotation of Earth on its axis
The Moon's gravitational pull

Correct answer: The tilt of Earth's axis as it orbits the Sun

Earth's seasons are caused by the 23.5° tilt of its axis. As Earth orbits the Sun, different hemispheres receive more direct sunlight at different times.

Question 5: What is the name of the supercontinent that existed approximately 300 million years ago?

Gondwana
Laurasia
Pangaea (Correct answer)
Rodinia

Correct answer: Pangaea

Pangaea was the single supercontinent that existed about 300-200 million years ago before breaking apart into today's continents.

Question 6: Which of the following is the correct order of the planets from closest to farthest from the Sun?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune (Correct answer)
Venus, Mercury, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
Mercury, Earth, Venus, Mars, Jupiter, Saturn, Uranus, Neptune
Mercury, Venus, Mars, Earth, Jupiter, Saturn, Uranus, Neptune

Correct answer: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

The correct order (using the mnemonic 'My Very Educated Mother Just Served Us Nachos') is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Question 7: What is the water cycle process where liquid water becomes water vapor?

Condensation
Precipitation
Evaporation (Correct answer)
Transpiration

Correct answer: Evaporation

Evaporation is the process by which liquid water (from oceans, lakes, etc.) is converted to water vapor through solar energy.

Question 8: A seismograph measures:

Atmospheric pressure
Earthquake intensity and seismic waves (Correct answer)
Ocean current speeds
Wind velocity

Correct answer: Earthquake intensity and seismic waves

A seismograph is an instrument used to detect and measure seismic waves caused by earthquakes or other ground movements.

Question 9: Which layer of the Sun produces the light and heat we receive on Earth?

The core
The radiation zone
The convection zone
The photosphere (Correct answer)

Correct answer: The photosphere

The photosphere is the visible surface of the Sun from which light and heat are emitted into space.

Question 10: What is the primary cause of ocean tides on Earth?

Earth's rotation
Solar wind
The Moon's gravitational pull (Correct answer)
Atmospheric pressure changes

Correct answer: The Moon's gravitational pull

Ocean tides are caused primarily by the Moon's gravitational pull, which creates bulges of water on the near and far sides of Earth.

Question 11: Which of the following is an example of a renewable resource?

Coal
Natural gas
Petroleum
Solar energy (Correct answer)

Correct answer: Solar energy

Solar energy is renewable because the Sun continuously produces energy. Coal, natural gas, and petroleum are fossil fuels — non-renewable resources formed over millions of years.

Question 12: What type of boundary exists where two tectonic plates move away from each other?

Convergent boundary
Transform boundary
Divergent boundary (Correct answer)
Subduction boundary

Correct answer: Divergent boundary

At a divergent boundary, two tectonic plates move apart, allowing magma to rise and create new crust — as seen at the Mid-Atlantic Ridge.

Question 13: What is the term for the point on Earth's surface directly above an earthquake's origin?

The focus
The epicenter (Correct answer)
The mantle
The seismic zone

Correct answer: The epicenter

The epicenter is the point on Earth's surface directly above the focus (hypocenter), where the earthquake originates underground.

Question 14: Which planet is known as the 'Red Planet'?

Jupiter
Venus
Mars (Correct answer)
Saturn

Correct answer: Mars

Mars is called the Red Planet because its surface is covered with iron oxide (rust), giving it a reddish appearance.

Question 15: In the rock cycle, which process converts igneous rock into sedimentary rock?

Melting and cooling
Heat and pressure
Weathering, erosion, and deposition (Correct answer)
Volcanic activity

Correct answer: Weathering, erosion, and deposition

Igneous rocks are broken down by weathering and erosion into sediments. These sediments are deposited and compacted over time to form sedimentary rock.

Question 16: What is the greenhouse effect?

The cooling of Earth due to clouds reflecting sunlight
The warming of Earth's surface due to atmospheric gases trapping heat (Correct answer)
The formation of ozone in the upper atmosphere
The process of photosynthesis in tropical forests

Correct answer: The warming of Earth's surface due to atmospheric gases trapping heat

The greenhouse effect occurs when greenhouse gases (CO₂, methane, water vapor) in the atmosphere absorb and re-emit infrared radiation, trapping heat near Earth's surface.

Question 17: What is a light-year?

The time it takes Earth to orbit the Sun
The distance light travels in one year (Correct answer)
A measure of a star's brightness
The time light takes to travel from the Sun to Earth

Correct answer: The distance light travels in one year

A light-year is a unit of distance equal to about 9.46 × 10¹² kilometers — the distance light travels in one year at 300,000 km/s.

Question 18: What causes a solar eclipse?

Earth passes between the Sun and Moon
The Moon passes between Earth and the Sun (Correct answer)
Earth passes between the Moon and Sun
Earth's shadow falls on the Moon

Correct answer: The Moon passes between Earth and the Sun

A solar eclipse occurs when the Moon passes directly between Earth and the Sun, blocking the Sun's light from reaching parts of Earth.

Question 19: Fossils are most commonly found in which type of rock?

Igneous rock
Metamorphic rock
Sedimentary rock (Correct answer)
Volcanic rock

Correct answer: Sedimentary rock

Fossils form in sedimentary rock. Organisms are buried in sediment which gradually hardens into rock, preserving the organism's remains or imprints.

Question 20: Which of the following BEST describes the Milky Way?

A single star system like our solar system
A spiral galaxy containing our solar system (Correct answer)
A type of nebula in deep space
The asteroid belt between Mars and Jupiter

Correct answer: A spiral galaxy containing our solar system

The Milky Way is a barred spiral galaxy containing billions of stars, including our Sun, along with our entire solar system.

Question 21: What is the term for water that flows over land into streams and rivers rather than soaking into the ground?

Groundwater
Precipitation
Runoff (Correct answer)
Evapotranspiration

Correct answer: Runoff

Runoff is water from precipitation that flows over the surface of the land and into streams, rivers, and eventually the ocean.

Question 22: Which of the following is the correct description of a lunar eclipse?

The Moon blocks the Sun's light from reaching Earth
Earth's shadow falls on the Moon (Correct answer)
The Moon disappears from view during a new moon phase
A solar storm disrupts the Moon's reflection

Correct answer: Earth's shadow falls on the Moon

A lunar eclipse occurs when Earth passes between the Sun and the Moon, causing Earth's shadow to fall on the Moon.

Question 23: What is the ozone layer and why is it important?

A layer of CO₂ that traps heat; it keeps Earth warm
A layer of O₃ in the stratosphere that absorbs harmful ultraviolet radiation from the Sun (Correct answer)
A cloud layer that produces rain; it is the water cycle
A layer of nitrogen that supports plant life

Correct answer: A layer of O₃ in the stratosphere that absorbs harmful ultraviolet radiation from the Sun

The ozone layer is a region in the stratosphere with high concentrations of ozone (O₃) that absorbs and blocks most of the Sun's harmful ultraviolet (UV) radiation.

Question 24: The three main types of rocks are:

Sedimentary, metallic, and volcanic
Igneous, organic, and crystalline
Igneous, sedimentary, and metamorphic (Correct answer)
Limestone, granite, and obsidian

Correct answer: Igneous, sedimentary, and metamorphic

The three main categories of rocks are igneous (formed from cooling magma/lava), sedimentary (formed from compacted sediments), and metamorphic (formed by heat and pressure).

Question 25: What force keeps planets in orbit around the Sun?

Magnetism
Nuclear force
Friction
Gravity (Correct answer)

Correct answer: Gravity

Gravity is the attractive force between masses. The Sun's massive gravity keeps planets in their orbital paths.

Question 26: Which cloud type is associated with thunderstorms and heavy rain?

Cirrus
Stratus
Cumulonimbus (Correct answer)
Altocumulus

Correct answer: Cumulonimbus

Cumulonimbus clouds are tall, dense clouds that extend through multiple levels of the atmosphere. They are associated with severe weather including thunderstorms, heavy rain, and hail.

Question 27: What is the approximate age of the universe?

4.5 billion years
7 billion years
13.8 billion years (Correct answer)
100 billion years

Correct answer: 13.8 billion years

Based on measurements of cosmic background radiation and the expansion rate of the universe, scientists estimate the universe is approximately 13.8 billion years old.

Question 28: What are the two main gases released during volcanic eruptions that affect climate?

Oxygen and nitrogen
Sulfur dioxide and carbon dioxide (Correct answer)
Hydrogen and helium
Ozone and methane

Correct answer: Sulfur dioxide and carbon dioxide

Volcanic eruptions release large amounts of sulfur dioxide (which can cool the climate by reflecting sunlight) and carbon dioxide (a greenhouse gas that can warm the climate).

Question 29: Which of the following correctly describes a convergent plate boundary?

Two plates moving apart, creating new crust
Two plates sliding past each other horizontally
Two plates colliding, often forming mountains or trenches (Correct answer)
A plate moving over a stationary hot spot

Correct answer: Two plates colliding, often forming mountains or trenches

At convergent boundaries, two tectonic plates collide. This can form mountain ranges (continent-continent collision), oceanic trenches, and volcanic arcs (ocean-continent collision).

Question 30: What is the most abundant element in Earth's crust?

Iron
Silicon
Aluminum
Oxygen (Correct answer)

Correct answer: Oxygen

Oxygen is the most abundant element in Earth's crust, making up approximately 46% by mass — most of it bonded with silicon in silicate minerals.

Question 31: The Coriolis effect refers to:

The bending of ocean currents and wind patterns due to Earth's rotation (Correct answer)
The gravitational pull of the Moon on Earth's oceans
The warming of ocean water in the Pacific during El Niño
The seasonal changes in wind direction

Correct answer: The bending of ocean currents and wind patterns due to Earth's rotation

The Coriolis effect is the deflection of moving objects (wind, ocean currents) due to Earth's rotation — to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Question 32: Which of the following best describes a star's life cycle in the correct order?

Nebula → Main sequence → Red giant → White dwarf (for Sun-like stars) (Correct answer)
Nebula → White dwarf → Red giant → Supernova
Main sequence → Nebula → Red giant → Black hole
Red giant → Nebula → White dwarf → Main sequence

Correct answer: Nebula → Main sequence → Red giant → White dwarf (for Sun-like stars)

A Sun-like star forms from a nebula, enters the main sequence (hydrogen fusion phase), expands to a red giant, then sheds its outer layers to become a white dwarf.

Question 33: What is the difference between weather and climate?

Weather is long-term; climate is short-term
Weather refers to short-term atmospheric conditions; climate refers to long-term patterns (Correct answer)
Weather only applies to deserts; climate only applies to oceans
They are the same thing

Correct answer: Weather refers to short-term atmospheric conditions; climate refers to long-term patterns

Weather describes short-term atmospheric conditions (temperature, precipitation) on a given day. Climate refers to the long-term patterns (averages) of weather in a region over decades.

Question 34: An El Niño event is characterized by:

Unusually cold sea surface temperatures in the central Pacific
Unusually warm sea surface temperatures in the central and eastern Pacific (Correct answer)
Increased volcanic activity in the Pacific Ring of Fire
A strengthening of trade winds across the Pacific

Correct answer: Unusually warm sea surface temperatures in the central and eastern Pacific

El Niño involves the periodic warming of sea surface temperatures in the central and eastern Pacific Ocean, disrupting normal weather patterns globally.

Question 35: What is the main difference between a meteor and a meteorite?

Meteors are larger than meteorites
A meteor burns up in the atmosphere; a meteorite reaches Earth's surface (Correct answer)
Meteorites are found in space; meteors land on Earth
They are the same object

Correct answer: A meteor burns up in the atmosphere; a meteorite reaches Earth's surface

A meteoroid entering Earth's atmosphere becomes a meteor (a 'shooting star'). If it survives and lands on Earth, it is called a meteorite.

Free GED Science Earth and Space Science Practice Test

Which layer of the Earth is the thinnest?