30+ Grade 12 Earth Science Worksheets 2024 - Free Printable

Problem Analysis and Solution

The task involves analyzing Figure 4, which shows three sites (Australia, South America, and Africa) with different layers labeled A–E for Site 1, F–I for Site 2, and J–O for Site 3. Each layer contains fossils of various organisms, and the goal is to answer questions based on this information.

#### Step 1: Understand the Fossils and Their Distribution
The key fossils are:
- Gastropod
- Coral
- Trilobite
- Fern
- Crinoid
- Ammonite

These fossils are distributed across the layers in each site. We need to identify their locations and use this information to answer the questions.

---

Question 39: Write which continent(s) the following fossils were found on

#### a) Fern
- Ferns are present in:
- Site 1 (Australia): Layer B
- Site 2 (South America): Layer G
- Site 3 (Africa): Layer N

Answer: Australia, South America, Africa

#### b) Trilobite
- Trilobites are present in:
- Site 1 (Australia): Layer C
- Site 2 (South America): Layer H
- Site 3 (Africa): Layer K

Answer: Australia, South America, Africa

#### c) Ammonite
- Ammonites are present in:
- Site 1 (Australia): Layer E
- Site 2 (South America): Layer I
- Site 3 (Africa): Layer O

Answer: Australia, South America, Africa

---

Question 40: Write how many layers at site 3 each fossil was found in

#### a) Ammonite
- At Site 3 (Africa), ammonites are found in Layer O.
- Count: 1 layer

Answer: 1

#### b) Fern
- At Site 3 (Africa), ferns are found in Layer N.
- Count: 1 layer

Answer: 1

#### c) Gastropod
- At Site 3 (Africa), gastropods are found in Layers J, L, M.
- Count: 3 layers

Answer: 3

#### d) Trilobite
- At Site 3 (Africa), trilobites are found in Layer K.
- Count: 1 layer

Answer: 1

#### e) Crinoid
- At Site 3 (Africa), crinoids are found in Layer M.
- Count: 1 layer

Answer: 1

---

Question 41: What is the index fossil?

An index fossil is a fossil that is widespread geographically but restricted to a short time period. To identify it:
1. Check if the fossil appears in every column (widespread).
2. Check if the fossil appears in only one layer per outcrop (short-lived).

- Gastropod: Appears in multiple layers (not short-lived).
- Coral: Appears in multiple layers (not short-lived).
- Trilobite: Appears in one layer per outcrop but not in every column.
- Fern: Appears in one layer per outcrop and in every column.
- Crinoid: Appears in one layer per outcrop but not in every column.
- Ammonite: Appears in one layer per outcrop and in every column.

Both fern and ammonite meet the criteria, but typically, ammonite is more commonly used as an index fossil due to its widespread presence and short-lived nature.

Answer: Ammonite

---

Question 42: Layers ________, ________, and ________ are all the same age

To determine which layers are the same age, we look for fossils that appear in corresponding layers across all three sites. For example:
- Layer B (Australia), Layer G (South America), and Layer N (Africa) all contain ferns.
- Layer C (Australia), Layer H (South America), and Layer K (Africa) all contain trilobites.
- Layer E (Australia), Layer I (South America), and Layer O (Africa) all contain ammonites.

Thus, the layers that are the same age are:
- B, G, N
- C, H, K
- E, I, O

We can choose any one set. Let's select the first set:

Answer: B, G, N

---

Question 43: The oldest layer is letter ________. The youngest layer is ________

To determine the oldest and youngest layers, we use the principle of superposition:
- The oldest layer is at the bottom of each site.
- The youngest layer is at the top of each site.

- Oldest layer: Layer A (Site 1), Layer F (Site 2), Layer J (Site 3).
- Youngest layer: Layer E (Site 1), Layer I (Site 2), Layer O (Site 3).

Since the question asks for a single letter, we can choose any representative from each site. Let's use the letters from Site 1:

Answer: Oldest: A; Youngest: E

---

Question 44: Layer F is ________ than layer J

- Layer F is at the bottom of Site 2.
- Layer J is at the top of Site 3.

Using the principle of superposition:
- Layer F is older than Layer J.

Answer: Older

---

Question 45: Layer H is ________ than layer D

- Layer H is in the middle of Site 2.
- Layer D is in the middle of Site 1.

Using the principle of superposition and the alignment of fossils:
- Layer H is younger than Layer D.

Answer: Younger

---

Question 46: Layer B is ________ than layer K

- Layer B is near the top of Site 1.
- Layer K is near the top of Site 3.

Using the principle of superposition and the alignment of fossils:
- Layer B is older than Layer K.

Answer: Older

---

Final Answers

1. Question 39:
- a) Fern: Australia, South America, Africa
- b) Trilobite: Australia, South America, Africa
- c) Ammonite: Australia, South America, Africa

2. Question 40:
- a) Ammonite: 1
- b) Fern: 1
- c) Gastropod: 3
- d) Trilobite: 1
- e) Crinoid: 1

3. Question 41: Ammonite

4. Question 42: B, G, N

5. Question 43: Oldest: A; Youngest: E

6. Question 44: Older

7. Question 45: Younger

8. Question 46: Older

Boxed Final Answer:
\[
\boxed{
\text{
1. a) Australia, South America, Africa \\
b) Australia, South America, Africa \\
c) Australia, South America, Africa \\
2. a) 1 \\
b) 1 \\
c) 3 \\
d) 1 \\
e) 1 \\
3. Ammonite \\
4. B, G, N \\
5. Oldest: A; Youngest: E \\
6. Older \\
7. Younger \\
8. Older
}}
\]