HiSET Science Study Guide: Earth Science
Earth science questions will assess your knowledge/understanding of:
- Properties of Earth materials
- Earth’s systems, geology, natural events, and tectonic forces
- Earth’s position in and relationship to the Solar System
- Basic astronomy
Since the HiSET science test puts the least emphasis on Earth science, we’ll spending just a few pages covering it, focusing primarily on key vocabulary you should know for test day.
Earth
The Earth is a dynamic, changing place where many forces interact.
Atmosphere: The atmosphere is the mix of gases animals breathe. Although animals need oxygen to survive, this element makes up only 20% of the atmosphere. Most of the atmosphere is nitrogen.
Core: At the Earth’s center is the core, a molten iron and nickel ball. Its slow rotation creates the magnetic field protecting Earth from harmful cosmic radiation.
Source: IsadoraofIbiza, CC BY 3.0, via Wikimedia Commons
Although no one has ever seen the Earth’s core, its existence has been confirmed through experimentation.
Fault Lines: Fault lines are where Earth’s tectonic plates meet. Friction between plates leads to earthquakes.
Global Warming/Greenhouse Effect: Rising carbon dioxide levels create a greenhouse effect, meaning less heat from the Sun radiates back into space. Manmade carbon dioxide emissions are causing Global Warming, a dramatic rise in Earth’s average temperature since the Industrial Revolution.
Magma: Magma is the molten rock trapped under the Earth’s crust. Scientists refer to magma as lava once it has breached the surface, such as in a volcanic eruption.
Ozone: Ozone is a molecule in the upper atmosphere that reduces the amount of ultraviolet radiation reaching the Earth’s surface. An ozone hole appeared over Antarctica in the 20th century due to the release of harmful chemicals.
Pangea: Nearly 300-million years ago, Pangea was a supercontinent containing all the Earth’s landmasses. Tectonic drift – the Earth’s tectonic plates drifting apart – separated the continents into what we see today.
Source: Osvaldocangaspadilla, Public domain, via Wikimedia Commons
Fossil records helped scientists prove Pangea’s existence.
Richter Scale: The Richter Scale measures earthquakes’ intensity. It ranges from 1.0-9.9. Each 1.0 step up in the scale represents 10x the power, meaning a 2.0 earthquake is 10x more powerful than a 1.0 earthquake, and a 3.0 earthquake is 100x more powerful than a 1.0 earthquake, etc.
Subduction: Subduction occurs at a fault line when one tectonic plate slides under another. Subduction is a primary cause of earthquakes.
Tsunami: Meaning “harbor wave” in Japanese, tsunamis are large and often destructive waves. Typical causes include landslides and tectonic plate movement.
Source: NGDC, CC BY-SA 3.0, via Wikimedia Commons
A Tsunami’s energy can take up to 20 hours to reach other parts of the world and can cause large waves thousands of miles away.
Water Cycle: The Water Cycle describes how water moves between glaciers, the atmosphere, rivers, and other bodies of water.
Weather/Climate
Weather and climate describe the same thing, but the difference is the time scale. A weather report may cover the coming week, but climate describes trends covering decades, centuries, and even longer.
Air Pressure: Air pressure is the pressure the atmosphere’s weight applies to an object. The higher someone travels up into the air, the less air pressure exists.
Gulf Stream: The Gulf Stream is a conveyor belt of hot water that travels from the Gulf of Mexico to the North Atlantic. The Gulf Stream is responsible for much of Europe’s temperate climate.
Seasons: A season is a division of the year based on the Earth’s tilt, daylight hours, changes in temperature, and changes in nature. Places close to the poles or Equator experience only one season.
Environment
The Earth’s environment is a dynamic place, one where humans have made a significant impact over the last two centuries.
Conservation: Conservation refers to using Earth’s natural resources in a sustainable way.
Nonrenewable Natural Resources: Nonrenewable natural resources (e.g., coal, oil, uranium) refer to resources that the Earth cannot replenish. The availability of these resources will only shrink over time.
Pollution: Pollution is the byproduct of industrial activity, such as industrial runoff or the exhaust produced by cars and factories. Pollution can cause short-term (e.g., cancer) and long-term (e.g., Global Warming) negative effects on people and communities.
Source: Mikael Häggström, Public domain, via Wikimedia Commons
These are just some of the effects that pollution can have on the human body.
Recycling: Recycling is an attempt to reduce the need for nonrenewable resources by repurposing existing products made from those resources. Examples include melting down plastic bottles to create new ones.
Renewable Natural Resources: Renewable natural resources are those that do replenish naturally. Examples include wind and hydroelectric power stations.
The Earth Over Time
The Earth has existed for nearly four-billion years. In that time, each geological era has left its mark on the Earth.
Abrasion: A process wherein a surface is worn down by something else traveling over it. During the last ice age 10,000 years ago, moving glaciers caused abrasion to mountain ranges that are still evident.
Deposition: The process by which sediment is deposited in layers. Sedimentary layers visible in rock is evidence that these places were once deep underwater.
Erosion: Erosion, the opposite of deposition, is the taking away of material from a place due to wind or water. Rocks on coastlines experience erosion due to the pounding waves.
Fossils: Fossils are the remains of organisms over 10,000 years old. A geological process replaced these organism’s living tissue with stone, preserving their shape and appearance. The oldest fossil is from an organism that lived over three-billion years ago.
Weathering: Weathering is a geological process wherein rocks break down over time due to interactions with the environment. This process turns large boulders into the sand between your toes.
Space
Space is a big place, and it’s the role of astronomers to study what’s beyond Earth’s thin atmosphere.
Asteroids: Asteroids are rocks floating through space. They are called meteors as they travel through the Earth’s atmosphere and meteorites once they land on the surface.
Astronomy: Astronomy is the study of outer space and its contents (e.g., planets, galaxies, black holes, etc.).
Black Hole: A black hole is an area of immense gravity that squishes everything that goes inside it into an infinitely small space called a singularity.
Source: EHT Collaboration, CC BY 4.0, via Wikimedia Commons
Black holes have such strong gravity that they can bend light’s path.
Comets: Comets are made up mostly of dust, small rocks, and ice. When they approach a star, they melt a little, causing a long tail made of gas and dust to form.
Galaxies: Galaxies are clusters of stars held together by gravity. The smallest galaxies contain only a few million stars, while the largest contain trillions of stars.
Inner Planets: The Inner Planets are those in the Solar System between the Sun and the Asteroid Belt. They include Mercury, Venus, Earth, and Mars.
Milky Way Galaxy: The Milky Way Galaxy is home to the Solar System. It contains 100-400-billion stars.
Outer Planets: The Outer Planets are planets in the Solar System that exist beyond the Asteroid Belt. They include the gas giants Jupiter, Saturn, Uranus, and Neptune.
Satellite: A satellite is a natural or manmade object in space that orbits an object with greater gravity. The Moon is Earth’s natural satellite.
Supernova: When large stars die, they collapse into themselves, causing an immense explosion known as a supernova. A typical supernova is billions of times brighter than the Sun.
