Finding Clues To Rock Layer | PDF - Free Printable

Let’s go through each question for Site 1 step by step, using the rock layer diagram and the fossil key.

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Question 1: What type of environment existed when Layers A and B were formed? What changed from layer B to layers D through layer G?

Look at the fossils in Layer A and Layer B (bottom two layers).
- Layer A has fish and shells → these live in water.
- Layer B also has fish and shells → still a water environment.

Now look at Layers D, E, F, G (above Layer B):
- Layer D: no fossils shown — but it’s labeled as “Extrusion (lava)” in the key.
- Layer E: same — extrusion (lava), no fossils.
- Layer F: dinosaur, plant, bird trace fossils → these are land animals/plants.
- Layer G: mammal, bird, plant → also land-based.

So:
→ Layers A and B = underwater (marine or lake) environment.
→ After Layer B, lava flowed (Layers C and E — wait, actually looking again: Layer C is striped with diagonal lines — that’s “Extrusion” too? Wait, let’s check the key.)

Wait — correction: In the diagram for Site 1:

Layer labels from bottom to top:
A → green, has fish & shells
B → pink, has fish & shells
C → blue stripes → according to key, this is “Extrusion (lava)”
D → yellow, has dinosaur, plant, bird traces
E → purple stripes → also “Extrusion (lava)”
F → light brown, has mammal, bird, plant
G → topsoil with grass

Actually, rechecking the image description: The user wrote answers already in red — but we’re solving it fresh.

But based on standard interpretation:

In Layer A and B: aquatic fossils → water environment.

From Layer B upward:
Layer C: lava flow (extrusion) → destroys any life/fossils
Layer D: now has dinosaur, plant, bird → land environment
Layer E: another lava flow
Layer F and G: more land animals and plants

So change: From water (A-B) → lava events (C, E) → then land environments (D, F, G)

Answer:
Water environment in A and B. Then lava covered the area (layers C and E), and after that, land environments developed where dinosaurs, birds, mammals, and plants lived.

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Question 2: Which layer is the oldest? How do you know?

In undisturbed rock layers, the bottom layer is oldest (Law of Superposition).

Layer A is at the very bottom → so it’s the oldest.

Answer: Layer A is oldest because it’s on the bottom — newer layers form on top of older ones.

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Question 3: What may have happened in layers C and E? (Look at the Key)

Key says: Diagonal striped pattern = “Extrusion (lava)”

So Layers C and E are lava flows that came out onto the surface.

Answer: Lava erupted and spread over the land, forming hard rock layers.

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Question 4: Why are there no fossils in layers C and E?

Lava is extremely hot — it burns up anything living or dead in its path. So if there were fossils below, they’d be destroyed. Also, nothing can survive or leave remains in molten lava.

Answer: The lava was too hot — it melted or burned any organisms or fossils that might have been there.

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Question 5: What kind of organism lived when layer F was formed?

Look at Layer F in Site 1 diagram: It shows symbols for mammal, bird, and plant (from key).

So: Mammals, birds, and plants lived during Layer F time.

Answer: Mammals, birds, and plants.

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Final Answer:

1. Layers A and B formed in a water environment (fish and shells found). From Layer B to G, the environment changed to land after lava flows (Layers C and E), allowing dinosaurs, birds, mammals, and plants to live there.

2. Layer A is the oldest because it is at the bottom — rock layers form from bottom to top.

3. Layers C and E were formed by lava extruding (flowing) onto the surface.

4. No fossils in C and E because the hot lava destroyed any existing fossils or organisms.

5. When Layer F formed, mammals, birds, and plants lived there.