ASVAB Study Guide ASVAB General Science

ASVAB Meteorology | Atmospheric Layers!

Feb 23rd, 2021
asvab meteorology

ASVAB Meteorology!

Meteorology is tested on the ASVAB General Science exam; a subject concerned with the study of the Earth’s atmosphere and how patterns of activity influence the weather that results.

Remember – on the General Science subtest, you will be asked:

  • 15 ASVAB test questions in 10-minutes for the CAT-ASVAB
  • 25 ASVAB test questions in 11-minutes for the Paper ASVAB

Therefore, you may be asked 2-3 questions alone on Earth science and meteorology. Nonetheless, to score high on the ASVAB and beat the competition, this is the kind of effort you must invest.

One of the most tested topics is atmospheric layers. That is because the atmosphere isn’t composed of one single, uniform layer. Instead, it is divided into distinct layers – each of which come with their own set of characteristics.

Below, we explore these layers – whilst also taking some time to learn about a layer that lies beyond our own atmosphere: the magnetosphere. Taken together, this ASVAB test prep will help you dominate this subject on the day of your exam.

Atmospheric Layers of the Earth

The Earth’s atmosphere is not one consistent layer.

It is instead comprised of many different layers – each of which is illustrated in the diagram below. Note the vastness of the atmosphere; how it extends from the surface of the Earth to over 500 miles up, toward the exosphere. The atmosphere is, then, the zone that comprises the layers that separate Earth from the boundary that is colloquially described as ‘outer space’.

asvab meteorology
Layers of Earth’s atmosphere: troposphere; stratosphere; mesosphere; thermosphere; and exosphere!
  • TROPOSPHERE – extends up to 7 miles from the base of the Earth and is the lowest layer of the Earth’s atmosphere. Airline jets operate within this range and it is also the range that life and standard weather patterns occupy.
  • STRATOSPHERE – above the ozone layer, extending 30 miles above Earth and is above the troposphere. Pollutants that reach the stratosphere can damage the ozone layer.
  • MESOSPHERE – this is the layer you typically see shooting stars, meteors that burn out as they hit the friction of the Earth’s upper atmosphere. The mesosphere extends 53 miles above the Earth’s surface.
  • THERMOSPHERE – the International Space Station (ISS) occupies this layer of the Earth’s atmosphere – extending 350 miles above. Other low orbit satellites also tend to occupy this later, too. Note the presence of the Kármán line that divides the thermosphere from the mesosphere. The Kármán line is an attempt to define a boundary between Earth’s atmosphere and outer space. This is important for legal and regulatory measures; aircraft and spacecraft fall under different jurisdictions and are subject to different treaties.
  • EXOSPHERE – the exosphere extends over 500 miles from the base of the Earth. At this point, gases and molecules are no longer retained by Earth but can instead dissipate into outer space.

There is also another broader layer known as the ionosphere.

This is not a single layer, per se – rather, it is a zone that defines the ionized part of Earth’s upper atmosphere, from about 48 km to 965 km altitude, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation.

Note that many ASVAB test practice questions ask about these layers, including the order of the layers. So, to remember the layers of the Earth’s atmosphere in order, consider the following mnemonic:

The Sun Manages Temperature Extremes”


  • T = Troposphere
  • S = Stratosphere
  • M = Mesosphere
  • Temp = Thermosphere
  • Ex = Exosphere

Though that completes our review of atmospheric layers, it is worth spending a moment to consider another layer that resides beyond our atmosphere.

Around the wider Earth is the magnetosphere.

As illustrated below (blue), the magnetosphere is enormously extended beyond Earth and is formed from the metals found in the Earth’s core – hence why we have a magnetic north pole and a magnetic south pole.

The function of the magnetosphere is to defend the Earth against the ionizing radiation of the solar wind. As the blizzard of the solar wind attempts to smash Earth with ionizing radiation, it is protected by this magnetospheric bubble – shielding Earth and its inhabitants from dangerous radiation; radiation that would not just affect the health of living organisms but also planetary health, in terms of climate temperature. If it were not for metals within the Earth’s core forming this magnetic sheath, the solar wind would otherwise have wrought havoc on this planet.

Magnetosphere; producing a magnetic shield around Earth that protects it from the solar wind!

Atmospheric Gases

The Earth’s atmosphere is composed of a variety of gases – and the combination of these gases is what helps to sustain life. Many people erroneously (but understandably) believe that oxygen has the highest concentration in the atmosphere, but this is not true. Instead, it is nitrogen – which makes up almost four-fifths of the gas composition of the atmosphere.

ASVAB test practice questions also ask about this composition. It is therefore important that you recall the following statistics – namely, that the Earth’s atmosphere is composed of:

  • 78 percent nitrogen
  • 21 percent oxygen
  • 0.93 percent argon
  • 0.04 percent carbon dioxide

However, the Earth’s atmosphere is also composed of a tiny number of what are known as trace gases – in other words, gases whose concentrations are extremely small. These include:

  • Methane
  • Neon
  • Krypton
  • Hydrogen
  • Helium

Taken together, these 9 gases – both major above and minor below – are what constitute almost all gas composition of the atmosphere. For the ASVAB test, it is important you keep these elements and breakdown in mind.

Take Home Message

ASVAB General Science can be a difficult subject.

Given the sheer volume of information to be learned, it often overwhelms many ASVAB test candidates. ASVAB General Science is important. Though it is not used to calculate your AFQT score, it does make up a surprisingly large number of MOS or line scores. To make it through to your career of choice, it is often imperative to score high on this subtest. And given the ubiquity and importance of science to many military careers, it is perhaps unsurprising that many candidates focus on this subtest more than others.

If you would like access to hundreds more study guides such as this, completing the ASVAB General Science subtest, log-in to your ASVAB Test Practice student portal to gain access to this module – which includes all study material, flashcards, practice questions, and an end-of-module examination.

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