Sea Floor Spreading Worksheet with labeled diagram illustrating the formation of new oceanic crust at mid-ocean ridges and the movement of tectonic plates.
Diagram showing the process of sea floor spreading, including the mid-ocean ridge, convection currents, and movement of tectonic plates.
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Show Answer Key & Explanations
Step-by-step solution for: 20+ Free Printable Sea Floor Spreading Worksheets
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Show Answer Key & Explanations
Step-by-step solution for: 20+ Free Printable Sea Floor Spreading Worksheets
To solve the problems related to the "Sea Floor Spreading Worksheet," let's address each question step by step using the provided diagram and geological concepts.
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- Answer: The feature shown at A is the Mid-Ocean Ridge.
- Explanation: The Mid-Ocean Ridge is a mountainous underwater range where tectonic plates diverge, allowing magma from the mantle to rise and cool, forming new oceanic crust. This is a key location for sea floor spreading.
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- Answer: The process shown at B is sea floor spreading.
- Explanation: Sea floor spreading occurs at the Mid-Ocean Ridge (A). Magma rises from the mantle through cracks in the Earth's crust, cools, and solidifies to form new oceanic crust. As more magma rises, the older crust is pushed away from the ridge, causing the ocean floor to spread outward. This process results in the creation of new oceanic crust and the movement of tectonic plates.
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- Answer: As new mantle material rises and forms new oceanic crust at the Mid-Ocean Ridge, the old oceanic crust moves away from the ridge. Eventually, the old oceanic crust reaches the edges of the ocean basin, where it sinks back into the mantle at subduction zones due to its greater density compared to the surrounding mantle material. This process is called subduction.
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- Answer: Three pieces of evidence supporting sea floor spreading are:
1. Magnetic Stripes on the Ocean Floor: The ocean floor has symmetrical magnetic stripes parallel to the Mid-Ocean Ridge. These stripes result from the Earth's magnetic field reversals over time, which are recorded in the cooling basalt as it forms at the ridge.
2. Age of Oceanic Crust: The oceanic crust is youngest at the Mid-Ocean Ridge and becomes progressively older as you move away from the ridge. This pattern supports the idea that new crust is formed at the ridge and spreads outward.
3. Volcanic Activity: Volcanoes and earthquakes are common along the Mid-Ocean Ridge, indicating active magma upwelling and plate divergence.
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- Answer: The process shown at C is subduction.
- Explanation: Subduction occurs when an oceanic plate collides with a continental plate or another oceanic plate. Due to the denser nature of the oceanic crust, it sinks beneath the less dense continental crust or another oceanic crust into the mantle. This process is driven by gravity and is responsible for the formation of deep ocean trenches (like the Mariana Trench) and volcanic arcs (e.g., the Andes).
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- Answer: The oldest rock on the ocean floor would be found farthest from the Mid-Ocean Ridge (A).
- Explanation: New oceanic crust is continuously formed at the Mid-Ocean Ridge. As the crust moves away from the ridge due to sea floor spreading, it ages. Therefore, the oldest oceanic crust is located at the edges of the ocean basins, near the subduction zones (C).
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- Answer: A device used to map the ocean floor is a sonar or multibeam echosounder.
- Explanation: Sonar (Sound Navigation and Ranging) uses sound waves to measure the depth and shape of the ocean floor. Multibeam echosounders provide detailed bathymetric maps by sending out multiple beams of sound simultaneously.
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- Answer: The feature at D is called a trench.
- Explanation: A trench is a deep depression in the ocean floor, typically formed at subduction zones where one tectonic plate is forced beneath another. The Mariana Trench is the deepest known trench on Earth.
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- Answer: The process is called sea floor spreading.
- Explanation: Sea floor spreading occurs at the Mid-Ocean Ridge, where magma rises from the mantle, cools, and forms new oceanic crust, continuously adding material to the ocean floor.
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- Answer: The process is called subduction.
- Explanation: Subduction occurs when an oceanic plate sinks into the mantle at a convergent boundary, typically at a subduction zone.
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- Answer: The chain of mountains is called the Mid-Ocean Ridge System.
- Explanation: The Mid-Ocean Ridge is a continuous mountain chain that runs through all the world's oceans, spanning approximately 65,000 kilometers. It is the longest mountain range on Earth, even though most of it lies underwater.
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1. Mid-Ocean Ridge
2. Sea floor spreading; new crust forms, pushing older crust away.
3. Old oceanic crust sinks into the mantle at subduction zones.
4. Magnetic stripes, age of oceanic crust, volcanic activity.
5. Subduction; denser oceanic crust sinks under continental or other oceanic crust.
6. Farthest from the Mid-Ocean Ridge.
7. Sonar/multibeam echosounder.
8. Trench.
9. Sea floor spreading.
10. Subduction.
11. Mid-Ocean Ridge System.
Final Boxed Answers:
\[
\boxed{
\text{1. Mid-Ocean Ridge} \\
\text{2. Sea floor spreading; new crust forms, pushing older crust away.} \\
\text{3. Old oceanic crust sinks into the mantle at subduction zones.} \\
\text{4. Magnetic stripes, age of oceanic crust, volcanic activity.} \\
\text{5. Subduction; denser oceanic crust sinks under continental or other oceanic crust.} \\
\text{6. Farthest from the Mid-Ocean Ridge.} \\
\text{7. Sonar/multibeam echosounder.} \\
\text{8. Trench.} \\
\text{9. Sea floor spreading.} \\
\text{10. Subduction.} \\
\text{11. Mid-Ocean Ridge System.}
}
\]
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1. What feature of the ocean floor is shown at A?
- Answer: The feature shown at A is the Mid-Ocean Ridge.
- Explanation: The Mid-Ocean Ridge is a mountainous underwater range where tectonic plates diverge, allowing magma from the mantle to rise and cool, forming new oceanic crust. This is a key location for sea floor spreading.
---
2. Describe the process shown occurring at B, and explain what results from this.
- Answer: The process shown at B is sea floor spreading.
- Explanation: Sea floor spreading occurs at the Mid-Ocean Ridge (A). Magma rises from the mantle through cracks in the Earth's crust, cools, and solidifies to form new oceanic crust. As more magma rises, the older crust is pushed away from the ridge, causing the ocean floor to spread outward. This process results in the creation of new oceanic crust and the movement of tectonic plates.
---
3. What happens to old oceanic crust as new mantle material rises from the mantle?
- Answer: As new mantle material rises and forms new oceanic crust at the Mid-Ocean Ridge, the old oceanic crust moves away from the ridge. Eventually, the old oceanic crust reaches the edges of the ocean basin, where it sinks back into the mantle at subduction zones due to its greater density compared to the surrounding mantle material. This process is called subduction.
---
4. If arrows on the figure show the ocean floor spreading from the ridge, what are three pieces of evidence scientists have found to support this idea?
- Answer: Three pieces of evidence supporting sea floor spreading are:
1. Magnetic Stripes on the Ocean Floor: The ocean floor has symmetrical magnetic stripes parallel to the Mid-Ocean Ridge. These stripes result from the Earth's magnetic field reversals over time, which are recorded in the cooling basalt as it forms at the ridge.
2. Age of Oceanic Crust: The oceanic crust is youngest at the Mid-Ocean Ridge and becomes progressively older as you move away from the ridge. This pattern supports the idea that new crust is formed at the ridge and spreads outward.
3. Volcanic Activity: Volcanoes and earthquakes are common along the Mid-Ocean Ridge, indicating active magma upwelling and plate divergence.
---
5. What process is shown occurring at C, and why does it occur?
- Answer: The process shown at C is subduction.
- Explanation: Subduction occurs when an oceanic plate collides with a continental plate or another oceanic plate. Due to the denser nature of the oceanic crust, it sinks beneath the less dense continental crust or another oceanic crust into the mantle. This process is driven by gravity and is responsible for the formation of deep ocean trenches (like the Mariana Trench) and volcanic arcs (e.g., the Andes).
---
6. Where would you expect to find the oldest rock on the ocean floor?
- Answer: The oldest rock on the ocean floor would be found farthest from the Mid-Ocean Ridge (A).
- Explanation: New oceanic crust is continuously formed at the Mid-Ocean Ridge. As the crust moves away from the ridge due to sea floor spreading, it ages. Therefore, the oldest oceanic crust is located at the edges of the ocean basins, near the subduction zones (C).
---
7. A device that scientists use to map the ocean floor is _______.
- Answer: A device used to map the ocean floor is a sonar or multibeam echosounder.
- Explanation: Sonar (Sound Navigation and Ranging) uses sound waves to measure the depth and shape of the ocean floor. Multibeam echosounders provide detailed bathymetric maps by sending out multiple beams of sound simultaneously.
---
8. The feature on the ocean floor at D is called _______ .
- Answer: The feature at D is called a trench.
- Explanation: A trench is a deep depression in the ocean floor, typically formed at subduction zones where one tectonic plate is forced beneath another. The Mariana Trench is the deepest known trench on Earth.
---
9. The process that continually adds new material to the ocean floor is called _______ .
- Answer: The process is called sea floor spreading.
- Explanation: Sea floor spreading occurs at the Mid-Ocean Ridge, where magma rises from the mantle, cools, and forms new oceanic crust, continuously adding material to the ocean floor.
---
10. The process by which the ocean floor sinks into the mantle is called _______ .
- Answer: The process is called subduction.
- Explanation: Subduction occurs when an oceanic plate sinks into the mantle at a convergent boundary, typically at a subduction zone.
---
11. The chain of mountains that extends into all of Earth’s oceans is the _______ .
- Answer: The chain of mountains is called the Mid-Ocean Ridge System.
- Explanation: The Mid-Ocean Ridge is a continuous mountain chain that runs through all the world's oceans, spanning approximately 65,000 kilometers. It is the longest mountain range on Earth, even though most of it lies underwater.
---
Final Answer Summary:
1. Mid-Ocean Ridge
2. Sea floor spreading; new crust forms, pushing older crust away.
3. Old oceanic crust sinks into the mantle at subduction zones.
4. Magnetic stripes, age of oceanic crust, volcanic activity.
5. Subduction; denser oceanic crust sinks under continental or other oceanic crust.
6. Farthest from the Mid-Ocean Ridge.
7. Sonar/multibeam echosounder.
8. Trench.
9. Sea floor spreading.
10. Subduction.
11. Mid-Ocean Ridge System.
Final Boxed Answers:
\[
\boxed{
\text{1. Mid-Ocean Ridge} \\
\text{2. Sea floor spreading; new crust forms, pushing older crust away.} \\
\text{3. Old oceanic crust sinks into the mantle at subduction zones.} \\
\text{4. Magnetic stripes, age of oceanic crust, volcanic activity.} \\
\text{5. Subduction; denser oceanic crust sinks under continental or other oceanic crust.} \\
\text{6. Farthest from the Mid-Ocean Ridge.} \\
\text{7. Sonar/multibeam echosounder.} \\
\text{8. Trench.} \\
\text{9. Sea floor spreading.} \\
\text{10. Subduction.} \\
\text{11. Mid-Ocean Ridge System.}
}
\]
Parent Tip: Review the logic above to help your child master the concept of seafloor spreading worksheet.
