Sea-floor spreading diagram illustrating the movement of oceanic crust and the formation of new oceanic material at mid-ocean ridges.
Diagram showing a cross-section of the ocean floor with labeled features including the continental shelf, continental slope, and oceanic ridge.
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Step-by-step solution for: Sea Floor Spreading Review And Reinforce Worksheet Answers - Fill ...
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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 geology or earth science textbook. The page includes a diagram of sea-floor spreading at a mid-ocean ridge and several questions related to the concept.
Since I can't view images directly, I’ll help you solve the problems based on the text you’ve provided. Let’s go through each question step by step and explain the answers clearly.
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The diagram likely shows:
- A mid-ocean ridge (divergent boundary) in the center.
- New oceanic crust forming at the ridge.
- Older crust moving away from the ridge on both sides.
- Layers labeled A, B, C, D, etc., representing different ages of oceanic crust.
- Magnetic anomalies (stripes) indicating reversals in Earth's magnetic field recorded in the ocean floor.
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#### 1. Name and describe the feature of the ocean floor shown at A.
Answer:
A 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 it solidifies at the ridge crest.
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#### 2. Describe the process shown occurring at B, and explain what results from this.
Answer:
At B, seafloor spreading is occurring. As tectonic plates move apart, magma rises from the mantle, fills the gap, and cools to form new oceanic crust. This process gradually pushes older crust outward from the ridge. The result is the creation of new oceanic crust and the expansion of the ocean floor.
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#### 3. What happens to old oceanic crust as new molten material rises from the mantle?
Answer:
As new molten material (magma) rises and solidifies at the mid-ocean ridge, it pushes the older oceanic crust away from the ridge. The old crust moves laterally (sideways) across the seafloor, becoming progressively older with distance from the ridge.
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#### 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 (reversals) – As new crust forms, iron-rich minerals align with Earth’s magnetic field. Periodic reversals of Earth’s magnetic field create alternating bands of normal and reversed polarity on the seafloor, symmetric around the ridge.
2. Age of oceanic crust – Seafloor rocks near the ridge are younger, and they get progressively older farther away, supporting the idea that crust spreads outward.
3. Ocean floor topography – The symmetrical pattern of ridges and valleys on either side of the mid-ocean ridge supports the idea of continuous crust formation and movement.
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#### 5. What process is shown occurring at C, and why does it occur?
Answer:
At C, subduction is occurring. This is where one tectonic plate is forced beneath another into the mantle. It occurs because older, denser oceanic crust sinks back into the mantle at convergent boundaries (like oceanic-oceanic or oceanic-continental), balancing the creation of new crust at the mid-ocean ridge.
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#### 6. A device that scientists use to map the ocean floor is a _________.
Answer: Sonar (Sound Navigation And Ranging) – uses sound waves to detect and map the ocean floor.
#### 7. The bottom of the ocean floor at C is called the _________.
Answer: Trench – a deep depression in the ocean floor formed at subduction zones.
#### 8. The process that continually adds new material to the ocean floor is called _________.
Answer: Seafloor spreading – the process where new oceanic crust is created at mid-ocean ridges and spreads outward.
#### 9. The process by which the ocean floor sinks into the mantle is called _________.
Answer: Subduction – the downward movement of one tectonic plate beneath another.
#### 10. A chain of underwater mountains along which sea-floor spreading occurs is a _________.
Answer: Mid-ocean ridge – a long mountain range under the ocean where new crust is formed.
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- Sea-floor spreading is the process by which new oceanic crust forms at mid-ocean ridges and pushes older crust outward.
- Evidence includes magnetic striping, age of rocks, and symmetrical topography.
- The cycle is balanced by subduction, where old crust sinks back into the mantle.
- This process is part of the larger theory of plate tectonics.
Let me know if you'd like a visual explanation or help with a specific part!
Since I can't view images directly, I’ll help you solve the problems based on the text you’ve provided. Let’s go through each question step by step and explain the answers clearly.
---
Diagram Description (Based on Standard Sea-Floor Spreading Model):
The diagram likely shows:
- A mid-ocean ridge (divergent boundary) in the center.
- New oceanic crust forming at the ridge.
- Older crust moving away from the ridge on both sides.
- Layers labeled A, B, C, D, etc., representing different ages of oceanic crust.
- Magnetic anomalies (stripes) indicating reversals in Earth's magnetic field recorded in the ocean floor.
---
Questions & Answers:
#### 1. Name and describe the feature of the ocean floor shown at A.
Answer:
A 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 it solidifies at the ridge crest.
---
#### 2. Describe the process shown occurring at B, and explain what results from this.
Answer:
At B, seafloor spreading is occurring. As tectonic plates move apart, magma rises from the mantle, fills the gap, and cools to form new oceanic crust. This process gradually pushes older crust outward from the ridge. The result is the creation of new oceanic crust and the expansion of the ocean floor.
---
#### 3. What happens to old oceanic crust as new molten material rises from the mantle?
Answer:
As new molten material (magma) rises and solidifies at the mid-ocean ridge, it pushes the older oceanic crust away from the ridge. The old crust moves laterally (sideways) across the seafloor, becoming progressively older with distance from the ridge.
---
#### 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 (reversals) – As new crust forms, iron-rich minerals align with Earth’s magnetic field. Periodic reversals of Earth’s magnetic field create alternating bands of normal and reversed polarity on the seafloor, symmetric around the ridge.
2. Age of oceanic crust – Seafloor rocks near the ridge are younger, and they get progressively older farther away, supporting the idea that crust spreads outward.
3. Ocean floor topography – The symmetrical pattern of ridges and valleys on either side of the mid-ocean ridge supports the idea of continuous crust formation and movement.
---
#### 5. What process is shown occurring at C, and why does it occur?
Answer:
At C, subduction is occurring. This is where one tectonic plate is forced beneath another into the mantle. It occurs because older, denser oceanic crust sinks back into the mantle at convergent boundaries (like oceanic-oceanic or oceanic-continental), balancing the creation of new crust at the mid-ocean ridge.
---
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) – uses sound waves to detect and map the ocean floor.
#### 7. The bottom of the ocean floor at C is called the _________.
Answer: Trench – a deep depression in the ocean floor formed at subduction zones.
#### 8. The process that continually adds new material to the ocean floor is called _________.
Answer: Seafloor spreading – the process where new oceanic crust is created at mid-ocean ridges and spreads outward.
#### 9. The process by which the ocean floor sinks into the mantle is called _________.
Answer: Subduction – the downward movement of one tectonic plate beneath another.
#### 10. A chain of underwater mountains along which sea-floor spreading occurs is a _________.
Answer: Mid-ocean ridge – a long mountain range under the ocean where new crust is formed.
---
✔ Summary of Key Concepts:
- Sea-floor spreading is the process by which new oceanic crust forms at mid-ocean ridges and pushes older crust outward.
- Evidence includes magnetic striping, age of rocks, and symmetrical topography.
- The cycle is balanced by subduction, where old crust sinks back into the mantle.
- This process is part of the larger theory of plate tectonics.
Let me know if you'd like a visual explanation or help with a specific part!
Parent Tip: Review the logic above to help your child master the concept of sea floor spreading worksheet.
