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ASVAB Practice Test · General Science

ASVAB Practice Test: Earth and Space Science Concepts

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Overview

This chapter covers the Earth itself, the air around it, and its place in the solar system. You will review the three main kinds of rock, the layers of the atmosphere and basic weather, and the movements of the Earth and Moon.

Rocks are grouped by how they form. Igneous rock forms when melted rock, called magma or lava, cools and hardens. Sedimentary rock forms when layers of sand, mud, or shells pile up and press together. Metamorphic rock forms when heat and pressure change an existing rock.

The atmosphere is the layer of gases around the Earth, and it is mostly nitrogen with a smaller share of oxygen. Weather happens in the lowest layer, the troposphere. The ozone layer, higher up in the stratosphere, blocks much of the sun's ultraviolet light.

The Earth spins on its axis once a day, which gives us day and night. It travels around the sun once a year. Seasons happen because the Earth's axis is tilted, not because the Earth gets closer to or farther from the sun. The Moon's pull is the main cause of ocean tides.

Key concepts

  • Three kinds of rock

    Igneous rock forms from cooled magma or lava. Sedimentary rock forms from layers of material pressed together. Metamorphic rock forms when heat and pressure change another rock.

    Memory tipFire, layers, or changed.

  • Atmosphere

    The layer of gases around the Earth. It is mostly nitrogen, with oxygen second. Weather happens in the lowest layer, the troposphere.

    Memory tipAir is mostly nitrogen, not oxygen.

  • Ozone layer

    A layer of ozone gas in the stratosphere that absorbs much of the sun's ultraviolet (UV) light, which protects living things.

    Memory tipOzone = sunscreen for the planet.

  • Rotation and revolution

    Rotation is the Earth spinning on its axis, about once a day, which causes day and night. Revolution is the Earth moving around the sun, about once a year.

    Memory tipRotate = spin (day). Revolve = orbit (year).

  • Seasons

    Seasons are caused by the tilt of the Earth's axis. The half tilted toward the sun gets more direct sunlight and has summer.

    Memory tipTilt, not distance.

  • Tides

    The regular rise and fall of the ocean. They are caused mainly by the Moon's gravity, with a smaller pull from the sun.

    Memory tipMoon pulls the water.

Often tested

  • Igneous rock forms from cooled magma or lava.
  • Earth's tilt causes the seasons.
  • Weather happens in the troposphere.
  • The air is mostly nitrogen.
  • The Moon is the main cause of tides.

Easy to confuse: Rotation vs. revolution

TermMovementResult
RotationEarth spins on its axisDay and night
RevolutionEarth travels around the sunOne year

3 sample questions

Verified practice questions from this unit.

Practice questionReviewedGeneral Science › Earth and Space Science★★★★☆

Question 1. Which type of rock forms when melted rock (magma or lava) cools and hardens?

  1. ① Sedimentary
  2. ② Clastic
  3. ③ Metamorphic
  4. ④ Igneous
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ④ Igneous

Key point: Igneous rock forms from cooled magma

Igneous rock forms when magma underground or lava on the surface cools and becomes solid. Granite and basalt are examples.

Wrong choices

  • (A) Sedimentary: Sedimentary rock forms from layers of sand, mud, or shells pressed together.
  • (B) Clastic: Clastic rock is a kind of sedimentary rock made of broken rock pieces.
  • (C) Metamorphic: Metamorphic rock forms when existing rock is changed by heat and pressure without fully melting.
Practice questionReviewedGeneral Science › Earth and Space Science★★★★☆

Question 2. What causes Earth to have seasons?

  1. ① Earth's changing distance from the Sun
  2. ② The phases of the Moon
  3. ③ The tilt of Earth's axis
  4. ④ Spots on the Sun
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ③ The tilt of Earth's axis

Key point: Earth's tilt causes the seasons

Earth's axis is tilted. As Earth orbits the Sun, each half of the planet takes turns leaning toward the Sun, getting more direct sunlight and longer days. That half has summer.

Wrong choices

  • (A) Earth's changing distance from the Sun: Distance is not the cause; Earth is actually closest to the Sun in early January, during northern winter.
  • (B) The phases of the Moon: Moon phases repeat about every month and do not cause seasons.
  • (D) Spots on the Sun: Sunspots come and go and do not cause yearly seasons.
Practice questionReviewedGeneral Science › Earth and Space Science★★★☆☆

Question 3. In which layer of the atmosphere does almost all weather happen?

  1. ① Troposphere
  2. ② Thermosphere
  3. ③ Mesosphere
  4. ④ Stratosphere
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ① Troposphere

Key point: Weather happens in the troposphere

The troposphere is the lowest layer of the atmosphere, the one we live in. It holds most of the air and water vapor, so clouds, rain, and storms form there.

Wrong choices

  • (B) Thermosphere: The thermosphere is very high and thin; it is where auroras appear.
  • (C) Mesosphere: The mesosphere is higher still and very dry; meteors burn up there.
  • (D) Stratosphere: The stratosphere is above the weather and contains the ozone layer.
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