Worksheet - Igneous Rocks #1 *EDITABLE* (WITH ANSWERS EXPLAINED) - Free Printable

Since I can't view or access images directly, I can't see the specific diagram or image you've uploaded. However, based on your description, it appears to be a Earth Science worksheet with questions related to igneous rocks, rock formation, and magma cooling rates.

Let me help you solve each question based on standard Earth Science knowledge and typical content found in such worksheets. If you can describe the diagrams (e.g., rock textures, grain sizes, or flowchart details), I can tailor the answers more precisely.

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Question 1: Which diagram below shows an area in which fine-grained igneous rocks are most likely to be found?

Answer:
Fine-grained igneous rocks form when magma cools quickly, usually on the Earth’s surface (extrusive). Rapid cooling doesn’t allow large crystals to grow.

✔ Look for a diagram showing lava flowing out onto the surface (like a volcano or lava field) — this would result in fine-grained rocks like basalt or rhyolite.

> Correct answer: The diagram that depicts lava erupting and cooling quickly at the surface.

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Question 2: Rock A in the diagram represents lava that has cooled rapidly at the surface of Earth. Which diagram and description represents rock B?

Assuming Rock B is a different type of igneous rock formed under different conditions:

- If Rock A = fine-grained (rapid cooling),
- Then Rock B might represent coarse-grained rock (slow cooling underground).

✔ So, Rock B is likely intrusive igneous rock formed from magma that cooled slowly beneath the surface.

> Correct answer: Diagram showing magma cooling slowly underground, forming large crystals → coarse-grained rock like granite.

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Question 3: Which sample was most likely formed from magma that cooled and solidified at the slowest rate?

Slow cooling → large crystals → coarse-grained texture

✔ Look for the sample with large visible mineral grains.

> Correct answer: The sample with large crystals (likely granite or similar).

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Question 4: The flowchart illustrates the change from melted rock to basalt.

Basalt is a fine-grained extrusive igneous rock.

So:
- Melted rock (magma) → cools quickly → solidifies on Earth's surface → forms basalt.

✔ The correct sequence should show:
1. Magma
2. Cool rapidly
3. Solidify on Earth’s surface
4. Form basalt

> Correct answer:
> b. rapidly, resulting in fine-grained minerals
> (Because basalt has fine grains due to rapid cooling)

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Question 5: What is the origin of fine-grained igneous rock?

Fine-grained rocks form from magma that cools quickly, typically on Earth’s surface.

✔ Answer: d. quickly, on Earth’s surface

> Explanation: When lava erupts and cools fast, atoms don’t have time to arrange into large crystals → small crystals → fine-grained texture.

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Question 6: Obsidian’s glassy texture indicates that it formed...

Obsidian is volcanic glass — no crystals because it cooled so fast that crystals couldn’t form.

✔ Answer: a. slowly, deep below Earth’s surface → ✘ (Wrong – slow cooling makes crystals)
→ b. slowly, on Earth’s surface → ✘ (Still too slow)
→ c. quickly, deep below Earth’s surface → ✘ (Deep = slow cooling)
→ d. quickly, on Earth’s surface → ✔

> Correct answer: d. quickly, on Earth’s surface

> Explanation: Obsidian forms when lava cools extremely rapidly (e.g., felsic lava flowing out of a volcano), preventing crystal growth → glassy texture.

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✔ Final Answers Summary:

| Question | Answer |
|--------|--------|
| 1 | Diagram showing lava erupting and cooling at surface |
| 2 | Diagram showing magma cooling slowly underground |
| 3 | Sample with large crystals (coarse-grained) |
| 4 | b. rapidly, resulting in fine-grained minerals |
| 5 | d. quickly, on Earth’s surface |
| 6 | d. quickly, on Earth’s surface |

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If you can describe the diagrams (e.g., what each labeled diagram shows), I can give even more precise feedback!