Educational worksheet on sea-floor spreading, featuring diagrams of mid-ocean ridges, sonar mapping, and pillow-shaped rocks as evidence of volcanic activity.

Sea-Floor Spreading Worksheet

#### Mapping the Mid-Ocean Ridge
1. The mid-ocean ridge is the longest chain of ________ in the world.
- Answer: mountains

2. Scientists mapped the mid-ocean ridge using _________.
- Answer: sonar

3. Sonar is a device that bounces sound waves off underwater objects and records it.

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#### Describing Sea-Floor Spreading
1. At the mid-ocean ridge, _________ material rises from the mantle and erupts. The molten material ___________, pushing ___________ rock to both sides of the ridge.
- Answer: magma, cools and solidifies, older

2. This process that ___________ is sea floor spreading.
- Answer: creates new oceanic crust and moves tectonic plates apart

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#### Evidence for Sea Floor Spreading: Pillow Shaped Rocks
1. In the 1960s scientists found evidence that ___________ is erupting along the ___________.
- Answer: magma, mid-ocean ridge

2. The presence of ___________ has showed that molten material has erupted again and again.
- Answer: pillow-shaped rocks

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Explanation of the Solution

#### Mapping the Mid-Ocean Ridge
- Mid-Ocean Ridge as Mountains: The mid-ocean ridge is indeed the longest mountain range in the world, stretching across the ocean floors.
- Sonar Mapping: Scientists use sonar technology to map the ocean floor by sending sound waves that bounce off underwater features and return to the ship, providing data about the depth and shape of the ocean floor.

#### Describing Sea-Floor Spreading
- Magma Eruption: At the mid-ocean ridge, magma rises from the mantle due to divergent plate boundaries where tectonic plates are moving apart.
- Cooling and Solidification: As the magma reaches the surface, it cools and solidifies, forming new oceanic crust.
- Pushing Older Rock: The newly formed crust pushes the older rock on either side of the ridge further away, demonstrating the process of sea-floor spreading.
- Sea-Floor Spreading Definition: This continuous creation of new crust and movement of tectonic plates is known as sea-floor spreading.

#### Evidence for Sea Floor Spreading: Pillow Shaped Rocks
- Magma Eruption Along Mid-Ocean Ridge: In the 1960s, scientists discovered that magma was erupting along the mid-ocean ridge, which explained the formation of new oceanic crust.
- Pillow-Shaped Rocks: When magma erupts underwater, it cools rapidly and forms distinctive pillow-shaped structures. These rocks provide evidence that magma has erupted repeatedly over time, supporting the theory of sea-floor spreading.

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Final Answer:

1. Mountains
2. Sonar
3. Magma, cools and solidifies, older
4. Creates new oceanic crust and moves tectonic plates apart
5. Magma, mid-ocean ridge
6. Pillow-shaped rocks

Boxed Final Answer:
\boxed{\text{Mountains, Sonar, Magma, cools and solidifies, older, Creates new oceanic crust and moves tectonic plates apart, Magma, mid-ocean ridge, Pillow-shaped rocks}}