Page 2 General Science Study Guide for the ASVAB

Earth and Space Science


Geology is the study of the earth, including such large applications as seismic shifts and the formation of mountains and such small applications as the formation of minute rock and mineral formations. Geology questions will likely be small, involving different types of minerals and natural formations such as mountains, plateaus, plains, and canyons. A rudimentary understanding of such structures and their creation will suffice.

Earth Structure

The Earth is made up of layers that differ in properties and function. The center of the Earth is the inner core, a solid, mostly metallic sphere or iron and nickel. Surrounding this is the outer core that is mostly liquid metal. Surrounding this is the mantle, a semisolid rock region. Between the mantle and the crust is layer of moving plates upon which the crust is held. Upon the crust are the continents and oceans.

Related terms to know: inner core, outer core, mantle, crust


The upper mantle and crust form the lithosphere, which is a collection of major plates upon which the crust sits. Due to pressure below the Earth’s surface, and the exchange of heat between the mantle and crust as well as the composition of these layers, the plates upon which the crust rests moves. This process is continental drift and explains the transition from the unified geography of Pangea to the current separation of the continents.

The boundaries between the plates experience heavy friction and geologic activity. Earthquakes and volcanoes are associated with the boundaries between tectonic plates.

Related terms to know: lithosphere, tectonic plates


Igneous rock, sedimentary rock, and metamorphic rock are the three main types of rocks.

Igneous rock is formed when magma or lava cools. A majority of the Earth’s crust is made up igneous rock. Sedimentary rock is made up of smaller sediments and inorganic material. Metamorphic rock is made when igneous or sedimentary rock are exposed and altered due to changes in temperature or pressure.

Related terms to know: igneous, sedimentary, metamorphic


The Earth’s major cycles are the: atmospheric, carbon, nitrogen, rock, and water cycle.

Changes in the Earth’s temperature cause changes in the air pressure in the atmosphere, which leads to the atmospheric cycle. This cycle is responsible for the dynamic weather of the planet.

The carbon cycle involves the passage of carbon through the ground, atmosphere, and water. Carbon, like nitrogen and water, is necessary in order for life to function.

The nitrogen cycle involves the transformation of nitrogen to its various useable forms. Nitrogen makes up a large part of the atmosphere, but in order for higher order organisms to use it, it must first be converted into a different form.

The rock cycle describes the way in which the three rock types transform from one type to another. These transformations take place when a rock undergoes a change in external surroundings.

The water cycle describes the movement of water to the atmosphere by way of evaporation and then from the atmosphere to the ground by way of precipitation.

Related terms to know: atmospheric cycle, carbon cycle, nitrogen cycle, water cycle


Meteorology is the study of the atmosphere and the ongoing changes that occur within the atmosphere. Much of meteorology aims to predict future weather and climate trends based on the current weather and climate.

Meteorologists study variables like air temperature, air pressure, wind speed, and humidity as well as the interactions among these variables to derive conclusions about the future conditions of the atmosphere.

Related terms to know: climate, weather, air pressure, air temperature

Astronomy and the Solar System

Astronomy is the study of celestial objects or, put simply, the study of the sky and heavenly bodies. To study for this portion of the general science exam, focus on simple facts and figures regarding the universe and its occupants.

A knowledge of all planets in the Solar System, for instance, is pivotal, as well as an understanding of the difference between different types of stars, planets, and moons. You should also include some time to study the effect planetary movements have upon the Earth and other members of the Solar System, such as the manner in which planets rotate around the Earth, the purpose of day and night, etc.

Our solar system is made up of the Sun and all of the space objects orbiting it, primarily the eight planets. The Sun, given its massive size exerts a strong gravitational force on the objects orbiting it.

The planets in order from nearest the sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Each planet has its own gravity and surrounding environment that differs depending on its distance from the Sun.

Related terms to know: planets, sun