Classifying Earth’s Physical Processes and Features

Good to see you again. Last time, you reviewed continents, oceans, Pangaea, Antarctica, and Lake Baikal. Now the focus is the Earth-science vocabulary in your study guide: the solid Earth, the air around it, height differences in landforms, molten rock, and the ways rock is changed or moved.

The goal is quick recognition: read a definition or example, then choose the correct term without being tricked by similar words such as magma/lava or weathering/erosion.

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Earth’s solid surface, air, and landform height

The lithosphere is Earth’s rigid, solid outer layer. It includes the crust and the brittle uppermost part of the mantle. Continents, ocean floors, mountains, and tectonic plates are part of the lithosphere.

The atmosphere is the layer of gases surrounding Earth. It is the air in which weather occurs. Do not confuse it with the lithosphere:

If the question describes…	Answer
Solid rock, crust, tectonic plates, outer solid Earth	LITHOSPHERE
Air, gases, clouds, wind, weather around Earth	ATMOSPHERE

Relief is the difference in elevation between the highest and lowest points of a landform or area. It tells you how much the land rises or falls.

For example, if a mountain’s base is at $400$ meters elevation and its summit is at $2,400$ meters elevation, its relief is:

$$2,400-400=2,000\text{ meters}$$

A flat plain has low relief. A steep mountain range or deep canyon area has high relief.

Spelling to memorize: RELIEF, not “releif.”
Spelling to memorize: LITHOSPHERE, not “litoshphere.”

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Magma and lava: one material, two locations

This is a very common multiple-choice distinction.

• Magma is molten rock below Earth’s surface.
• Lava is magma that has erupted and reached Earth’s surface.

The material does not become a different substance simply because it erupts. Its name changes because its location changes.

Use this memory rule:

Location of molten rock	Correct term
Beneath Earth’s surface, in the crust or mantle	MAGMA
On Earth’s surface, flowing from a volcano	LAVA

Your original study list says, “Molten rock that can form in the mantle and rise through the crust?” The accurate answer is MAGMA, not lava. Once that molten rock reaches the surface, it becomes LAVA.

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Chemical weathering versus glacial erosion

Rock can be changed in place, or it can be moved. The difference matters.

Weathering breaks down or changes rock where it is.
Erosion wears away and moves rock or sediment to another location.

Chemical weathering changes a rock through chemical reactions. Acid rain is the standard test example: acidic water reacts with minerals in rock and can dissolve or alter them. The rock’s chemical makeup changes; this is more than simply cracking a rock into smaller pieces.

A glacier is a huge mass of ice that slowly moves over land. As it moves, it erodes rock mainly in two ways:

1. Abrasion: rocks frozen into the ice scrape and grind the bedrock below, much like sandpaper.
2. Plucking: ice freezes onto cracked bedrock and pulls pieces of rock away as the glacier moves.

The correct answer to “A glacier is an example of what type of erosion?” is usually:

GLACIAL EROSION or ICE EROSION

A glacier moves downhill partly because of gravity, but gravity is not the best classification answer when the question asks for the agent of erosion. The erosion is caused by moving ice.

Use this sorter:

Example	Correct classification	Why
Acid rain reacts with a marble building	CHEMICAL WEATHERING	Chemicals alter or dissolve minerals.
Tree roots crack a sidewalk	Mechanical or biological weathering	Rock breaks in place.
A river carries sand downstream	EROSION	Sediment is moved.
Ice drags rocks across bedrock	GLACIAL EROSION	Moving ice scrapes and removes rock.
A chunk of rock breaks underground before an eruption	Not lava yet	It is below the surface; molten rock there is magma.

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Rapid multiple-choice review

Try to answer before looking at the line below each question.

1. The solid, rocky outer layer of Earth that includes the crust and uppermost mantle is the:
A. atmosphere
B. lithosphere
C. hydrosphere
D. biosphere

B. LITHOSPHERE

2. Which Earth system is made mainly of gases surrounding the planet?
A. lithosphere
B. atmosphere
C. mantle
D. relief

B. ATMOSPHERE

3. The difference between an area’s highest and lowest elevations is called:
A. weathering
B. relief
C. lava
D. atmosphere

B. RELIEF

4. Molten rock beneath Earth’s surface is called:
A. lava
B. magma
C. crust
D. ash

B. MAGMA

5. When magma erupts onto Earth’s surface, it is called:
A. lava
B. relief
C. lithosphere
D. chemical weathering

A. LAVA

6. Acid rain reacting with and dissolving minerals in rock is an example of:
A. chemical weathering
B. glacial erosion
C. lava flow
D. relief

A. CHEMICAL WEATHERING

7. A glacier carrying rocks that scrape across bedrock causes:
A. atmospheric erosion
B. chemical weathering
C. glacial erosion
D. volcanic eruption

C. GLACIAL EROSION

8. Which statement is accurate?
A. Lava is molten rock underground.
B. Magma is molten rock on Earth’s surface.
C. Magma becomes lava when it reaches Earth’s surface.
D. The lithosphere is made of gases.

C. MAGMA BECOMES LAVA WHEN IT REACHES EARTH’S SURFACE.

9. Which situation shows erosion rather than weathering?
A. Acid rain dissolves part of a statue.
B. Water carries broken rock pieces down a stream.
C. Ice expands in a crack and splits a rock.
D. Roots break apart a boulder.

B. WATER CARRIES BROKEN ROCK PIECES DOWN A STREAM.

10. A mountain range with very tall peaks and deep valleys has:
A. high relief
B. low relief
C. no lithosphere
D. chemical weathering only

A. HIGH RELIEF

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Flashcard finish

Read the prompt, say the answer aloud, then check.

• Solid outer Earth: crust plus uppermost mantle — LITHOSPHERE
• Layer of gases around Earth — ATMOSPHERE
• Difference between highest and lowest elevation — RELIEF
• Molten rock below the surface — MAGMA
• Molten rock at the surface — LAVA
• Rock altered by reactions, such as acid rain — CHEMICAL WEATHERING
• Rock worn away and moved by a glacier — GLACIAL EROSION
• Glacial scraping by rocks in the ice — ABRASION
• Glacier pulling away blocks of bedrock — PLUCKING

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Key takeaways

For the test, keep these distinctions sharp:

• LITHOSPHERE: solid outer Earth, including crust and upper mantle.
• ATMOSPHERE: gases surrounding Earth.
• RELIEF: difference between high and low elevation.
• MAGMA: molten rock underground.
• LAVA: magma at Earth’s surface.
• CHEMICAL WEATHERING: rock chemically changed, such as by acid rain.
• GLACIAL EROSION: moving ice scrapes and pulls away rock.

Next, you will connect plate movement to earthquakes, volcanoes, tsunamis, Alaska, the Ring of Fire, Chile, the New Madrid Seismic Zone, and Old Faithful.