This section takes a look at an important area of your science study – Earth Science – particularly in the areas of the atmosphere, meteorology, and astronomy.
Posted in 1st December, 2014 | General ScienceEarth Science
Earth Science
This section is made up of many interconnected topics. For example, we will be studying aspects of astronomy, geology, meteorology, and Earth’s atmosphere. Together, it will give you a solid grounding in the lead up to the ASVAB General Science exam. Questions in earth science appear relatively frequently, so you must become acquainted with the basic facts in each of the topics outlined previously. In comparison to the sections on biology, chemistry, and physics, the earth science component is much simpler to understand, so all you need to do is become familiar with the relevant material. At the end of this study guide, you will have the opportunity to test your knowledge of all the material covered here.
It’s also worth emphasizing that all material referenced here is examinable. The purpose of this guide is, after all, to act as a convenient summary of everything you need to know. First, we will spend a significant amount of time on astronomy, before moving onto Earth-specific topics, before finally concluding with the structure and function of our atmosphere. This all-inclusive section provides all the resources you need to answer any of the relevant ASVAB questions.
A Space to Learn
Our planet, the Earth, is only one of eight planets that occupy our Solar System. At the center of our Solar System is, of course, the Sun – a tremendously large celestial object that provides all the light and heat necessary to nourish life-permitting conditions on this planet. The eight planets of our Solar System include (starting from nearest to the Sun): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. In 2005, Pluto was demoted and is no longer considered a planet but is, instead, considered to be what’s known as a dwarf planet. These eight planets orbit around the common center of mass – the Sun – and orbit due to the powerful strength of the Sun’s gravitational field.
Our Earth doesn’t orbit around the Sun in a circle but, rather, it orbits in an elliptical form. An ellipse is like a slightly elongated circle. It takes 365 days for the Earth to orbit around the Sun – a period known as a year. Although, it’s not “exactly 365” days! It takes 365.25 days to be exact and, as a consequence, we have a leap year every 4 years once we add on this extra day (0.25 x 4 = 1). This day will render February 29 days long as opposed to its usual 28 days. The next leap year is in 2016. The Earth is tilted at an angle of 23.5°, which is the direct cause of the different seasons we experience.
These eight planets are divided into two groups of four. The inner four planets (Mercury, Venus, Earth, and Mars) are rocky planets – hence why they are known as the terrestrial planets. This contrasts with the outer four planets (Jupiter, Saturn, Uranus, and Neptune) which are known as Jovian planets (or Gas Giants) – due to their high preponderance of gas a constituent of their structure. Not all of these planets have moons – as Mercury and Venus can testify. The rest of the planets have moons with Jupiter having up to 64+ moons! In fact, it’s the planet Jupiter that contains the so-called Galilean moons – Callisto, Io, Europa, and Ganymede. This is because these moons were discovered by Galileo Galilei, the astronomer who discovered them in the 1600s.
Our moon is important as it’s responsible for producing the tides, as well as influencing the way the seasons operate. It takes 27.3 days for the moon to orbit around the Earth.
When the moon sits exactly between the Earth and the Sun, an event known as the Solar Eclipse occurs. This happens as the moon passes across the Sun, masking it and producing a spectacular display. If the moon, on the other hand is at the opposite side of the Earth, then a lunar eclipse will occur, as the Earth is shielding the moon from the light of the Sun.
- Solar Eclipse Order: Earth – Moon – Sun
- Lunar Eclipse Order: Moon – Earth – Sun
Although, the moon isn’t the only rock you should be concerned about. Many other rocks, known as meteors, travel throughout space and might, one day, enter the Earth’s atmosphere. If the meteor is small enough, it will burn up in the Earth’s atmosphere due to the severe effects of friction – this burning is what we see as a shooting star. Some meteors, though, are sufficiently large to avoid burning up in the atmosphere and, if the rock happens to touch the ground, we now term it a meteorite. Meteors can come from many different regions of space; one of the most common being the asteroid belt. This is a belt of rocks that orbit between the planets Mars and Jupiter. Occasionally, one of these rocks will become dislodged, hurling itself toward Earth at an incredibly fast rate.
The vast majority of rocks that occupy the asteroid belt are not meteors though but are, in fact, asteroids. So, what is the difference between an asteroid and a meteor? An asteroid is defined as a minor planet, as they tend to be significantly larger than a meteor, while also remaining in some form of a stable orbit around the Sun. This contrasts with meteors that are smaller and enter the Earth’s atmosphere. Some asteroids carry their own moons, whereas meteors do not. Another rock you should be aware of is the comet. Unlike asteroids and meteors, comets are icy bodies that arrive from the depths of outer space, and they tend to carry a tail. These subtle distinctions are worth bearing in mind for the ASVAB General Science exam.
This is pretty much everything you will need to know to pass the astronomy questions of your exam. As we discussed at the beginning of this section, it’s not a complex subject to understand but, instead, involves a considerable amount of memory work. Try not to be phased by this, as you will get to grips with the terminology in time. You need to stay on top of the earth science by planning your study in the weeks and months ahead, catering to one heading at a time until you complete the entire section. We will now turn our attention to rocks and weather – as these two sections form a significant part of the questions you can expect on the day of your ASVAB General Science exam.
As you learn the science of Earth, try to think of the scientific principles underpinning each process. This will aid your overall understanding of the topic as you study.
Diving into Earth
There are two main subjects you need to become familiar with: geology and meteorology. Geology is the study of rocks and their place in the Earth. This contrasts with meteorology which studies the weather and atmosphere of Earth. Both of these subjects will appear in some form in your exam. We will first begin by looking at some basic geology, which involves understanding the different layers and structure of Earth. Upon completing this, we will take a quick look at basic weather patterns and the layers of the atmosphere. This rigorous grounding will prepare you for the needs of the ASVAB General Science exam.
Our planet is constantly changing, including its internal components. It would be wrong to think of our internal planet as dead and unmoving, when it’s actually quite a dynamic environment. This is reflected in the numerous layers that characterize our planet. The top layer – the part you and I walk along each and every day – is known as the crust. From a geological perspective, this crust is known as the lithosphere. The layer just beneath the crust is called the mantle, with this layer composing the vast majority of the mass of our Earth. Geologically, the upper mantle is known as the asthenosphere. Below the mantle, we find the very center of our planet, which is known as the core.
The core of our planet consists of iron and nickel, which contrasts against the mantle which mostly contains magma. When magma rises, it creates cracks in the crust known as faults. These faults are often responsible for many earthquakes, such as the San Andreas Fault in California. From a terminological perspective, magma is different from lava. When magma reaches the surface of the Earth it becomes known as lava, but magma itself refers to its presence in layers such as the mantle. Magma also reaches the surface of the Earth through volcanic activity – with the latter acting as hot springs for the spewing of lava. When enough pressure builds within the crust and upper mantle of the Earth, it needs to release this pressure – something volcanoes help to alleviate.
The crust, or lithosphere, is not uniform. It is composed of many plates known as tectonic plates. These tectonic plates glide along the lithosphere/asthenosphere, though at an incredibly slow rate – as little as half an inch per year. If you were to crack a boiled egg a few times, you would end up with an appearance somewhat analogous to the tectonic plates of our planet. Sometimes these plates rub against one another, and this friction is experienced as an earthquake. Other times, the plates collide – with one plate sliding underneath the other – in the same way some teeth tend to slip beneath others. This slipping process is known as subduction. Subduction is responsible for producing vast mountain ranges, as land is displaced and is forced to rise. Mount Everest in the Himalayas, for example, was produced by subduction.
That’s a lot of terminology, so let’s take a quick review to catch up on some key parts:
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- There are three main layers of Earth: Crust – Mantle – Core. The crust is known as the lithosphere, while the upper mantle is known as the asthenosphere.
- The mantle is characterized by the presence of magma. This magma reaches the Earth through faults in the Earth’s crust, or through volcanic activity. When magma reaches the surface of the Earth, it becomes known as lava.
- The surface of the Earth is divided into numerous tectonic plates. These can rub against each other to form earthquakes, or collide via subduction to produce volcanoes.
Today’s Weather
Earth is not the only planet with an atmosphere, but it’s the only one you will need to learn. This section is particularly relevant for those training to enlist in the US Air Force, as weather remains a central part of many operations. To put it simply, we could not have any weather were it not for the atmosphere. The presence of an atmosphere is an absolute necessity if we are to experience any weather whatsoever. Weather is, at the same time, quite a complex phenomenon to understand, as conditions often vary and causes can be difficult to discern. Nonetheless, much progress has been made, particularly in the area of understanding the layers of the atmosphere itself.
The table below details the five main layers of the Earth’s atmosphere, beginning with the lowest layer, the Troposphere, before concluding with the outermost layer, the Exosphere.
| # | Layer | Distance | About |
|---|---|---|---|
| 01 | Troposphere | 0-7 miles | The lowest layer which contains most of the weather we experience. |
| 02 | Stratosphere | 7-30 miles | Ozone layer can be found here, where absorption of solar UV radiation also takes place. |
| 03 | Mesosphere | 31-50 miles | Meteors tend to burn up in this layer. |
| 04 | Thermosphere | 50-440 miles | The International Space Station orbits through this layer. |
| 05 | Exosphere | 440 miles > | This layer extends out into space, and so has no exiting boundary layer. |
So, the vast majority of the weather we experience occurs in the troposphere, that layer of the atmosphere that extends from ground level up to approximately 7 miles above. The weather we experience is greatly influenced by temperature variation. Let’s think of land and water, for example, and the way temperature influences it. Land heats up considerably faster than water during the day, while at night the land cools considerably faster than water. The formation of cold masses of air and cold masses of air is significant. Cold masses are, after all, denser than warm masses. If something is denser it will also have greater pressure, and so cold masses have greater pressure than warm masses.
Air will always try to reach a balance, or equilibrium. As a result, air will move from regions of high pressure (cold masses) to regions to low pressure (warm masses). This movement of air is what we experience as wind. We can measure the pressure of the atmosphere by using an instrument known as the barometer. You might even have one of these in your home. Either way, you can appreciate the significance of the formation of cold and warm masses. The next step is to think about this on a global scale. Air masses formed in the north and south of our planet are cold, while air masses forming at the equator are warm. This means, at some point, these air masses will interact. The question is – how?
This interaction of air masses is known as a front. It’s important to note that the cold and warm masses do not mix but, instead, form a weather front. The formation of this front will determine the type of weather we receive. When cold air bumps into warm air, it will form a cold front, while when warm air bumps into a cold air mass; this will form a warm front. What is the difference between a cold front and a warm front anyway? Well, a cold front will thrust the warm air upwards into the sky, resulting in heavy rainfall. A warm front will pass its air over the cold air mass, causing much lighter rainfall. In other words, how a front forms will determine the type of weather we receive. This front is created by the formation of cold air masses and warm air masses for the reasons outlined earlier.
This might be somewhat of a simplification though. After all, we observe many different cloud types such that it can be challenging to keep on top of them all. For your ASVAB General Science exam, you will be expected to become familiar with the most common cloud types, while being able to determine the type of cloud from its very name. This is actually much easier than you might think. Take a look at the list below, which details the type and style of clouds you are expected to know:
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- Cirrus clouds are the highest type of cloud – you tend to witness this type of cloud on warm days as thin wispy clouds high into the sky.
- Stratus clouds are flat thick clouds often seen on overcast days. They tend to produce drizzle-type or cool weather.
- Cumulus clouds are cauliflower-shaped clouds, appearing quite fluffy and separated. We often see this cloud type on relatively nice days.
If a cloud uses the prefix “Nimbo”, such as Nimbostratus, it refers to a cloud type that will cause rain. If, however, the cloud type uses the prefix “Alto”, such as “Altostratus”, it refers to clouds quite high up, but not as high as cirrus clouds. These are the only cloud types you are expected to know, so it shouldn’t become too difficult to familiarize yourself with each and every one of them. When trying to learn the various cloud types, always dissect the name of the cloud. From its name, we can easily discern its meaning. Cirrostratus is, for example a high cloud (‘cirrus’), that’s broadly flat and thick. Nimbocumulus, on the other hand, refers to a raincloud (‘nimbo’) that’s shaped in a fluffy cauliflower way (‘cumulus’).
This completes our study of the earth science component of your ASVAB General Science exam. Along with the biology and physical science components, you are now ready to take this examination. You must invest considerable time into each of these sciences, as you can be sure your questions will derive from the material you study here. The best approach at this stage is to take part in numerous self-assessment quizzes. This will test your existing knowledge of the sciences, while acting as a blueprint for areas you need to study more. Then, when you study a little more, take another self-assessment quiz and, hopefully, your science grade will rise. Yes – it will take practice, but you will undoubtedly succeed in the long run if you put in the time, effort, and ceaseless dedication.
The final section of this ASVAB General Science study guides summarizes
what you have learned and where you should go from here.
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