Earth's Internal Structure, Seismic Waves, and Space Exploration

Comprehensive practice flashcards covering Earth's internal layers, seismic wave propagation and shadow zones, small Solar System bodies (asteroids, comets, meteoroids, dwarf planets), and space exploration technologies.

What is the correct sequence of Earth's four main layers from the outside inward?

$$\text{Crust} \rightarrow \text{Mantle} \rightarrow \text{Outer Core} \rightarrow \text{Inner Core}$$

How is Earth's crust described?

Earth's thin, solid outermost layer of solid rock where we live, which is extremely thin compared with the mantle.

What are the key characteristics of Earth's mantle?

The mantle is the thick layer of hot rock beneath the crust and represents the thickest compositional layer of Earth.

What is the state of matter and composition of Earth's outer core?

A liquid layer made mainly of iron and nickel that surrounds the inner core and is much thicker than the inner core.

How is Earth's inner core characterized?

The solid, extremely hot central part of Earth composed of solid iron and nickel.

What is the lithosphere composed of?

The lithosphere consists of the crust and the rigid uppermost mantle.

What is the asthenosphere?

A weaker, slowly deforming part of the upper mantle located beneath the lithosphere.

What are seismic waves, and why do scientists study them?

Seismic waves are vibrations that travel through Earth when an earthquake occurs. Scientists study how these waves travel to understand Earth's interior.

What are the primary characteristics of P-waves (Primary waves)?

They are the fastest seismic body waves, push and pull particles, travel through solids, liquids, and gases, and can bend or change speed when entering different materials.

What are the key characteristics of S-waves (Secondary waves)?

They are transverse body waves that travel slower than P-waves, move particles side to side or up and down at a right angle to the direction of travel, travel through solids only, and cannot travel through liquids and gases.

What are surface waves, and are Love waves body waves or surface waves?

Surface waves travel along Earth's surface and usually cause the strongest shaking and much of the damage near the surface. Love waves are a type of surface wave, not a body wave.

What is the difference between an earthquake's focus and its epicenter?

The focus is the point inside Earth where an earthquake begins, whereas the epicenter is the point on Earth's surface directly above the focus.

What is a fault in Earth's crust?

A crack or fracture in Earth's crust where rocks move.

What is a discontinuity in geology?

A boundary between Earth layers where seismic-wave speed or behavior changes.

What causes the S-wave shadow zone?

Direct S-waves are not detected in this area because S-waves cannot pass through the liquid outer core.

What causes the P-wave shadow zone?

Direct P-waves are not detected in this area because P-waves bend strongly as they enter the outer core.

What two seismic wave observations provide evidence that Earth's outer core is liquid?

1. S-waves disappear beyond certain distances because they cannot travel through the liquid outer core.
2. P-waves slow down and bend sharply as they enter the outer core.

What is an asteroid, and where are most asteroids in the main Asteroid Belt found?

A rocky or metallic object that orbits the Sun. Most asteroids in the main Asteroid Belt are located between Mars and Jupiter.

What is a comet, and what occurs when it approaches the Sun?

An object made of ice, dust, and rocky material. When it approaches the Sun, its ice changes directly into gas via sublimation, which helps form a cloud called the coma and sometimes a visible tail.

How are meteoroids, meteors, and meteorites distinguished from one another?

A meteoroid is a small rocky or metallic object in space; a meteor is the streak of light in the atmosphere (commonly called a shooting star) when gas heats up; a meteorite is the piece of space debris that survives passage through the atmosphere and reaches the ground.

Why are comets scientifically important?

Comets preserve ancient ice and dust from the early Solar System, enabling scientists to study the conditions and substances present when the Solar System formed.

What causes the annual Perseid meteor shower, and when does it take place?

The Perseids occur every year around August when Earth crosses the debris stream left behind by Comet Swift-Tuttle (the comet does not need to pass close to Earth each year).

What four criteria define a dwarf planet?

1. Orbits the Sun.
2. Is nearly round because of its own gravity.
3. Has not cleared other objects from its orbital neighborhood.
4. Is not a moon.

Where are the dwarf planets Ceres, Pluto, Eris, and Makemake located?

Ceres is located in the main Asteroid Belt between Mars and Jupiter; Pluto and Makemake are in the Kuiper Belt; and Eris is a distant dwarf planet beyond Neptune.

What is a space probe, and how does it gather and transmit data?

An uncrewed spacecraft sent to investigate conditions in space. It carries scientific instruments (cameras, sensors, measuring devices) close to a target to gather data and sends it back to Earth via radio signals without necessarily needing to land.

What types of radiation do optical, radio, infrared, ultraviolet, X-ray, and gamma-ray telescopes detect?

Optical: visible light; Radio: radio waves; Infrared: infrared radiation (which can pass through dust); Ultraviolet: ultraviolet radiation from hot objects; X-ray: X-rays from extremely hot and energetic sources; Gamma-ray: gamma rays from very energetic explosions and extreme cosmic activity.

Why are space telescopes useful compared to ground-based telescopes?

Earth's atmosphere absorbs some wavelengths of electromagnetic radiation and distorts incoming light. Space telescopes can observe wavelengths that are difficult or impossible to observe from the ground.

What six properties of distant celestial objects can be inferred by analyzing their light?

Composition, Temperature, Motion (toward or away), Distance, Brightness, and Physical features (size, shape, and surface characteristics).

What distinguishes crewed space technology from uncrewed space technology?

Crewed space technology includes spacecraft or facilities used by astronauts (such as the International Space Station space laboratory), whereas uncrewed space technology operates without people aboard (such as space probes, robotic rovers, and artificial satellites).

Why is a radar-equipped orbiter the best technology to map the surface of Venus?

Venus has thick clouds that block ordinary visible-light views of much of its surface, but radar can penetrate the cloud cover and provide information about the surface.

What technologies are best suited to measure Martian soil directly versus inferring water vapor around an exoplanet?

A lander or rover with scientific instruments is best to measure Martian soil directly, while a telescope with suitable instruments for analyzing light is best to infer water vapor around an exoplanet.