Sea-Floor Spreading diagram showing the process of new oceanic crust forming at mid-ocean ridges and moving outward.
Diagram of the ocean floor showing layers of sediment and rock, illustrating sea-floor spreading with arrows indicating the movement of tectonic plates.
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Step-by-step solution for: Sea Floor Spreading Review And Reinforce Worksheet Answers - Fill ...
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Show Answer Key & Explanations
Step-by-step solution for: Sea Floor Spreading Review And Reinforce Worksheet Answers - Fill ...
It looks like you've uploaded a worksheet titled "Sea-Floor Spreading" from a science textbook, and it includes a diagram of the ocean floor with labeled features (A, B, C) and several questions related to plate tectonics. Since I can't view images directly, I’ll help you solve the problem based on the description and typical content of such worksheets.
Let’s go through each question step by step using standard geological knowledge about sea-floor spreading.
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The diagram likely shows:
- A mid-ocean ridge (at point A) where new oceanic crust is formed.
- Oceanic crust moving away from the ridge toward points B and C.
- Magnetic striping (normal/reversed polarity) on either side of the ridge, showing symmetrical patterns.
- A cross-section of the ocean floor showing layers of sediment overlying basaltic crust.
---
#### 1. Name and describe the feature of the ocean floor shown at A.
Answer:
At point A, the feature is the mid-ocean ridge. It is an underwater mountain range formed by tectonic plates pulling apart (divergent boundary). Magma rises from the mantle, cools, and forms new oceanic crust as the plates move away from each other.
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#### 2. Describe the process shown occurring at B, and explain what results from this.
Answer:
At point B, the process is sea-floor spreading. As the plates move apart at the mid-ocean ridge, magma rises and solidifies to form new oceanic crust. This new crust pushes older crust outward, causing the seafloor to spread. The result is the creation of new oceanic crust and the gradual widening of the ocean basin.
---
#### 3. What happens to old oceanic crust as new molten material rises from the mantle?
Answer:
As new molten material rises at the mid-ocean ridge, it pushes the existing oceanic crust away from the ridge. The older crust moves laterally and eventually may be subducted at a convergent boundary or eroded over time.
---
#### 4. The arrows on the figure show the ocean floor spreading from the ridge. What are three kinds of evidence scientists have found to support this idea?
Answer:
Scientists use these three main types of evidence:
1. Magnetic striping: Symmetrical patterns of normal and reversed magnetic polarity in oceanic crust on either side of the mid-ocean ridge, matching Earth's past magnetic reversals.
2. Age of the ocean floor: Rocks near the ridge are younger; they become progressively older farther from the ridge.
3. Seafloor topography and sediment thickness: The seafloor is youngest and deepest at the ridge, and gets older and shallower (with more sediment) as you move away.
---
#### 5. What process is shown occurring at C, and why does it occur?
Answer:
At point C, the process is subduction (if it's near a convergent boundary), or cooling and sinking of the oceanic crust. As the oceanic crust moves away from the ridge, it cools, becomes denser, and sinks lower into the mantle. If it meets another plate, it may be forced beneath it (subduction). This occurs due to gravity and density differences — cold, dense oceanic crust sinks back into the mantle.
> *(Note: If point C is just far from the ridge but not near a trench, then it's simply cooling and thickening, not necessarily subducting.)*
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#### 6. A device that scientists use to map the ocean floor is a _________.
Answer:
Sonar (Sound Navigation And Ranging)
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#### 7. The bottom of the ocean floor at C is called the _________.
Answer:
Oceanic trench (if subduction is occurring) or abyssal plain (if it's flat deep-sea area).
> Most likely: Abyssal plain or deep ocean basin — but if there’s a trench, it would be trench.
> Based on context, likely: Abyssal plain — the flat, deep area of the ocean floor far from the ridge.
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#### 8. The process that continually adds new material to the ocean floor is called _________.
Answer:
Sea-floor spreading
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#### 9. The process by which the ocean floor sinks into the mantle is called _________.
Answer:
Subduction
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#### 10. A chain of underwater mountains along which sea-floor spreading occurs is a _________.
Answer:
Mid-ocean ridge
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| Question | Answer |
|--------|--------|
| 1 | Mid-ocean ridge – a mountain range formed by diverging tectonic plates where new crust forms. |
| 2 | Sea-floor spreading – new crust forms at the ridge and pushes older crust outward. |
| 3 | Old crust is pushed aside and may be subducted or cooled and sink. |
| 4 | Magnetic striping, age of rocks, sediment thickness. |
| 5 | Cooling/sinking or subduction – due to density increase as crust cools. |
| 6 | Sonar |
| 7 | Abyssal plain (or oceanic trench, depending on context) |
| 8 | Sea-floor spreading |
| 9 | Subduction |
| 10 | Mid-ocean ridge |
---
If you can provide more specific details about the diagram (like labels or what’s at point C), I can refine the answers further!
Let’s go through each question step by step using standard geological knowledge about sea-floor spreading.
---
Diagram Description (Inferred):
The diagram likely shows:
- A mid-ocean ridge (at point A) where new oceanic crust is formed.
- Oceanic crust moving away from the ridge toward points B and C.
- Magnetic striping (normal/reversed polarity) on either side of the ridge, showing symmetrical patterns.
- A cross-section of the ocean floor showing layers of sediment overlying basaltic crust.
---
Questions and Answers:
#### 1. Name and describe the feature of the ocean floor shown at A.
Answer:
At point A, the feature is the mid-ocean ridge. It is an underwater mountain range formed by tectonic plates pulling apart (divergent boundary). Magma rises from the mantle, cools, and forms new oceanic crust as the plates move away from each other.
---
#### 2. Describe the process shown occurring at B, and explain what results from this.
Answer:
At point B, the process is sea-floor spreading. As the plates move apart at the mid-ocean ridge, magma rises and solidifies to form new oceanic crust. This new crust pushes older crust outward, causing the seafloor to spread. The result is the creation of new oceanic crust and the gradual widening of the ocean basin.
---
#### 3. What happens to old oceanic crust as new molten material rises from the mantle?
Answer:
As new molten material rises at the mid-ocean ridge, it pushes the existing oceanic crust away from the ridge. The older crust moves laterally and eventually may be subducted at a convergent boundary or eroded over time.
---
#### 4. The arrows on the figure show the ocean floor spreading from the ridge. What are three kinds of evidence scientists have found to support this idea?
Answer:
Scientists use these three main types of evidence:
1. Magnetic striping: Symmetrical patterns of normal and reversed magnetic polarity in oceanic crust on either side of the mid-ocean ridge, matching Earth's past magnetic reversals.
2. Age of the ocean floor: Rocks near the ridge are younger; they become progressively older farther from the ridge.
3. Seafloor topography and sediment thickness: The seafloor is youngest and deepest at the ridge, and gets older and shallower (with more sediment) as you move away.
---
#### 5. What process is shown occurring at C, and why does it occur?
Answer:
At point C, the process is subduction (if it's near a convergent boundary), or cooling and sinking of the oceanic crust. As the oceanic crust moves away from the ridge, it cools, becomes denser, and sinks lower into the mantle. If it meets another plate, it may be forced beneath it (subduction). This occurs due to gravity and density differences — cold, dense oceanic crust sinks back into the mantle.
> *(Note: If point C is just far from the ridge but not near a trench, then it's simply cooling and thickening, not necessarily subducting.)*
---
Building Vocabulary – Fill in the blanks:
#### 6. A device that scientists use to map the ocean floor is a _________.
Answer:
Sonar (Sound Navigation And Ranging)
---
#### 7. The bottom of the ocean floor at C is called the _________.
Answer:
Oceanic trench (if subduction is occurring) or abyssal plain (if it's flat deep-sea area).
> Most likely: Abyssal plain or deep ocean basin — but if there’s a trench, it would be trench.
> Based on context, likely: Abyssal plain — the flat, deep area of the ocean floor far from the ridge.
---
#### 8. The process that continually adds new material to the ocean floor is called _________.
Answer:
Sea-floor spreading
---
#### 9. The process by which the ocean floor sinks into the mantle is called _________.
Answer:
Subduction
---
#### 10. A chain of underwater mountains along which sea-floor spreading occurs is a _________.
Answer:
Mid-ocean ridge
---
✔ Final Summary of Answers:
| Question | Answer |
|--------|--------|
| 1 | Mid-ocean ridge – a mountain range formed by diverging tectonic plates where new crust forms. |
| 2 | Sea-floor spreading – new crust forms at the ridge and pushes older crust outward. |
| 3 | Old crust is pushed aside and may be subducted or cooled and sink. |
| 4 | Magnetic striping, age of rocks, sediment thickness. |
| 5 | Cooling/sinking or subduction – due to density increase as crust cools. |
| 6 | Sonar |
| 7 | Abyssal plain (or oceanic trench, depending on context) |
| 8 | Sea-floor spreading |
| 9 | Subduction |
| 10 | Mid-ocean ridge |
---
If you can provide more specific details about the diagram (like labels or what’s at point C), I can refine the answers further!
Parent Tip: Review the logic above to help your child master the concept of ocean floor worksheet.
