I'll work through this worksheet step by step to help you understand the answers.
## Working Through the Questions:
Question 1: Based on the theory of plate tectonics, would you expect to find any new rock or old rock at an oceanic ridge? Explain why.
Looking at the diagram and information provided:
- Oceanic ridges are where plates move apart (divergent boundaries)
- When plates separate, magma rises from the mantle
- This magma cools and hardens to form NEW rock
- Therefore, at oceanic ridges, we would find NEW rock being created
Answer for Question 1: You would expect to find
new rock at an oceanic ridge because these are divergent boundaries where plates move apart, allowing magma to rise from the mantle and cool into new rock.
Question 2: Based on the theory of plate tectonics, would you expect to find any new rock or old rock at an oceanic trench? Explain why.
From the diagram and text:
- Oceanic trenches occur at convergent boundaries
- At convergent boundaries, one plate is pushed under another (subduction)
- The subducting plate sinks into the mantle
- These areas have the OLDEST oceanic crust that is about to be recycled
- New rock isn't created here; instead, old rock is destroyed/recycled
Answer for Question 2: You would expect to find
old rock at an oceanic trench because these are convergent boundaries where older oceanic crust is being subducted (pushed down) into the mantle.
Question 3: In the Pacific Ocean, there is a plate boundary between two tectonic plates: the Pacific Plate, which contains some of the oldest oceanic crust on Earth, and the Nazca Plate. The Nazca Trench, the deepest oceanic trench on Earth, is located at the plate boundary between these two plates. What type of plate boundary is this? How do you know?
From the information given:
- There's a deep oceanic trench (Nazca Trench)
- One plate has very old crust
- Trenches form at convergent boundaries
- The description matches what happens when plates converge and one subducts under the other
Answer for Question 3: This is a
convergent boundary. I know this because:
1. There is an oceanic trench present (Nazca Trench)
2. Trenches only form at convergent boundaries where plates come together
3. One plate is being subducted under the other, creating the deepest trench
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Final Answer:
1. New rock - Oceanic ridges are divergent boundaries where plates move apart, allowing magma to rise and create new rock.
2. Old rock - Oceanic trenches are convergent boundaries where older oceanic crust is subducted into the mantle.
3. Convergent boundary - The presence of the Nazca Trench (the deepest oceanic trench) indicates this is a convergent boundary where the Pacific Plate and Nazca Plate are coming together, with one plate subducting beneath the other.
Parent Tip: Review the logic above to help your child master the concept of tectonic plates worksheet.
