Seafloor Spreading 1.27.12
The discovery of seafloor spreading lead to more questions about Earth's crust. If new crust is constantly being formed, why is the Earth now getting larger? Harry Hess determined the ocean crust is constantly being recycled. As new crust is formed at the seafloor ridges, the older crust is being reclaimed into magma by descending into ocean trenches.
Draw a diagram of what occurred in your seafloor spreading.
Draw a diagram of what occurred in your seafloor spreading.
1. Magma is pushed up through the ridges in the seafloor to form new oceanic crust. As each new layer emerges, the prior layer is pushed away from the ridge. If the space between the tables is the ridge and the craft sticks represent the magma, then which sticks represent the oldest portion and which sticks represent the youngest portion of oceanic crust? Explain your answer using the numbers on the magma sticks.
The first sticks represent the oldest magma, because it is there while the new magma comes up from the ridge. Stick number 11 represents the youngest portion of the magma, because it is the last to come up from the ridge.
2. The addition of new oceanic crust is one mechanism that applies force to tectonic plates. The model did not accurately show the direction of force during the creation of new crust. How could you change the model to show that the magma is pushed out at the ridge (rather than pulled)?
Instead of pulling out at the ends, you could push the magma sticks out from the trench. From the space between, you can push it to show the direction of force.
3. Describe what occurred as you continued to slide the strips of oceanic crust (craft sticks) away from the ridge.
As you slide the magma sticks out, they go down into the trench, representing continental crust.
4. What do you think will happen to the oceanic crust that is pulled down into the trench?
The crust that is pulled down melts and is turned back into magma. The magma then comes back up through the ridges.
5. Harry Hess described this process as a recycling of the ocean basins. As new crust is created at the ridge, a process called subduction occurs at the trenches. Why must subduction occur at the trenches in order for Hess's idea to be correct?
Subduction is when the crust sinks down into trenches and melts into magma. The magma then comes back up through the ridges and the process starts again.
6. Is crust created or destroyed at the trenches?
The crust is destroyed because it melts into magma to start the process again.
The first sticks represent the oldest magma, because it is there while the new magma comes up from the ridge. Stick number 11 represents the youngest portion of the magma, because it is the last to come up from the ridge.
2. The addition of new oceanic crust is one mechanism that applies force to tectonic plates. The model did not accurately show the direction of force during the creation of new crust. How could you change the model to show that the magma is pushed out at the ridge (rather than pulled)?
Instead of pulling out at the ends, you could push the magma sticks out from the trench. From the space between, you can push it to show the direction of force.
3. Describe what occurred as you continued to slide the strips of oceanic crust (craft sticks) away from the ridge.
As you slide the magma sticks out, they go down into the trench, representing continental crust.
4. What do you think will happen to the oceanic crust that is pulled down into the trench?
The crust that is pulled down melts and is turned back into magma. The magma then comes back up through the ridges.
5. Harry Hess described this process as a recycling of the ocean basins. As new crust is created at the ridge, a process called subduction occurs at the trenches. Why must subduction occur at the trenches in order for Hess's idea to be correct?
Subduction is when the crust sinks down into trenches and melts into magma. The magma then comes back up through the ridges and the process starts again.
6. Is crust created or destroyed at the trenches?
The crust is destroyed because it melts into magma to start the process again.