Charting the Ocean Floor - Holly Hedrick | Library | Formative - Free Printable

The image you've provided is a worksheet titled "Charting the Ocean Floor", which explains how scientists measure ocean depth using sonar technology and provides data to create a profile of the Atlantic Ocean floor. The task involves interpreting and plotting depth data across different longitudes to visualize underwater features like the Mid-Atlantic Ridge.

Since there's no explicit question on the front page, I’ll assume the goal of this worksheet is:

> To plot the ocean depth data on a graph to create a cross-sectional profile of the Atlantic Ocean floor and identify major features such as the Mid-Atlantic Ridge.

Let’s walk through the solution step by step.

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🔍 Step 1: Understand the Data

We are given a table with two columns:
- Longitude (°W) – decreasing from 64°W to 1°W (moving eastward)
- Ocean Depth (m) – the depth at each longitude

This represents a transect (a straight-line cross-section) of the ocean floor from west to east across the Atlantic Ocean.

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📈 Step 2: Plotting the Data

To chart the ocean floor:
1. Use longitude (°W) on the horizontal axis (x-axis).
2. Use ocean depth (m) on the vertical axis (y-axis).
3. Since depth increases downward, the y-axis should increase downward (like a topographic profile).
- Alternatively, you can invert the scale so that deeper depths appear lower on the graph.

> 💡 Tip: Label the x-axis from 64°W to 1°W (left to right).
> Label the y-axis from 0 m (surface) down to ~5000 m (deepest point).

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✔ Step 3: Identify Key Features

Now let's analyze the depth values:

| Longitude (°W) | Depth (m) |
|----------------|-----------|
| 64 | 0 |
| 60 | 90 |
| 55 | 131 |
| 50 | 71 |
| 48 | 3511 |
| 45 | 4023 |
| 40 | 3804 |
| 35 | 4170 |
| 33 | 3438 |
| 30 | 3072 |
| 28 | 1755 |
| 27 | 2194 |
| 25 | 3145 |
| 20 | 4243 |
| 15 | 4609 |
| 10 | 4975 |
| 5 | 4316 |
| 4 | 145 |
| 1 | 0 |

#### Observations:
- At 64°W and 1°W, depth is 0 m → these are likely near continental shelves (landmasses).
- From 64°W to 48°W, depth increases rapidly → descending into deep ocean.
- Maximum depth (~4975 m) occurs at 10°W.
- Then depth decreases toward 1°W → rising back to shallow water.

#### What does this shape suggest?

This profile shows:
- A deep trench or ridge in the middle of the Atlantic.
- The Mid-Atlantic Ridge is a mid-ocean ridge where tectonic plates diverge.
- It is typically elevated (shallow) in the center and deeper on both sides.

But wait — here we see the deepest point at 10°W, not the shallowest.

Wait! Let’s double-check:
At 10°W, depth = 4975 m → very deep.
At 48°W, depth = 3511 m → also deep.

But at 5°W, depth = 4316 m, then drops sharply to 145 m at 4°W and 0 m at 1°W.

That suggests something unusual.

Let’s look more closely:

- From 64°W to 48°W: shallow → deep (continental shelf → abyssal plain)
- From 48°W to 10°W: very deep (over 4000 m), peaking at 4975 m at 10°W
- Then drops rapidly to 145 m at 4°W, then 0 m at 1°W

That sudden drop from 4316 m to 145 m between 5°W and 4°W seems suspicious.

But wait — could this be due to data error? Or perhaps it's real?

Actually, this data appears to have an inconsistency.

Let’s re-express the trend:

| Longitude | Depth (m) | Trend |
|----------|-----------|-------|
| 64°W | 0 | Shallow |
| ... | ... | ... |
| 48°W | 3511 | Deepening |
| 45°W | 4023 | Deeper |
| 40°W | 3804 | Slightly shallower |
| 35°W | 4170 | Deeper |
| 33°W | 3438 | Shallower |
| 30°W | 3072 | Shallower |
| 28°W | 1755 | Much shallower |
| 27°W | 2194 | Deeper again |
| 25°W | 3145 | Deeper |
| 20°W | 4243 | Very deep |
| 15°W | 4609 | Deepest |
| 10°W | 4975 | Peak depth |
| 5°W | 4316 | Shallower |
| 4°W | 145 | ⚠️ Sudden drop |
| 1°W | 0 | Land |

➡️ The sudden drop from 4316 m to 145 m between 5°W and 4°W is not geologically realistic for the Atlantic Ocean.

This suggests either:
- A typo in the data (maybe 145 was meant to be 4145?)
- Or the profile crosses a continental shelf near Europe.

But the Mid-Atlantic Ridge is typically in the center, and its summit is elevated (not the deepest point).

So what’s going on?

Let’s check the depth pattern:

- The deepest point is at 10°W (4975 m)
- Then it rises sharply to 145 m at 4°W → that would imply a steep slope from deep ocean to shallow continental shelf.

But this doesn’t match the expected structure of the Mid-Atlantic Ridge.

Wait — maybe the data is reversed?

No, the longitude goes from 64°W to 1°W, which is west to east across the Atlantic.

In reality:
- The Mid-Atlantic Ridge runs roughly along ~30°W to 10°W, but it's a ridge, meaning it's shallower in the middle.

But here, the maximum depth is at 10°W, not a peak.

So unless this is a trench, it’s not consistent.

But the Mid-Atlantic Ridge is a mountain range, not a trench.

So why is the depth increasing?

Ah! Here's the key:

👉 The data may be mislabeled or inverted.

But looking again: Depth = 0 at 64°W and 1°W, and very deep in the middle.

That actually makes sense!

- 64°W is near North America
- 1°W is near Europe
- The Mid-Atlantic Ridge is in the middle, but it's underwater, so the ocean floor is deep around it, but the ridge itself is shallower.

Wait — if the ridge is shallow, then depth should be less over the ridge.

But in this data, depth is greatest at 10°W.

That contradicts expectations.

Unless... the ridge is not the highest point in this section.

But let’s calculate the average depth:

- Most points are over 3000 m
- The minimum depth is 0 m at both ends
- The maximum depth is 4975 m at 10°W

But in reality, the Mid-Atlantic Ridge has peaks at ~2000–3000 m, while the abyssal plains are ~4000–5000 m.

So the deepest parts are away from the ridge, not on it.

Thus, this data does not show a ridge, but rather a deep basin with shallow edges.

But the Mid-Atlantic Ridge is a mountain chain, so it should be shallower than the surrounding seafloor.

So why is depth increasing toward the center?

Wait — perhaps the data is correct, but the ridge is not visible because it's not the shallowest point?

No — let’s reconsider.

Maybe the ridge is located near 27–28°W, where depth is 1755 m, which is much shallower than nearby areas.

Let’s find the lowest depth (i.e., shallowest ocean floor):

- At 28°W: 1755 m
- At 27°W: 2194 m
- At 30°W: 3072 m
- At 33°W: 3438 m
- At 35°W: 4170 m

So 1755 m at 28°W is the shallowest point in the central Atlantic.

That suggests the Mid-Atlantic Ridge is near 28°W.

But earlier we thought the deepest was at 10°W.

So the profile shows:
- Deep water near Americas (64°W)
- Rises to a shallow ridge at ~28°W
- Then deepens again toward Europe

But the data shows depth increasing from 64°W to 48°W, then peaks at 10°W, then drops to 145 m at 4°W.

Wait — that means:
- From 64°W to 48°W: depth increases → descending
- From 48°W to 28°W: depth varies, but 1755 m at 28°W is relatively shallow
- Then from 28°W to 10°W: depth increases again → deeper
- Then drops sharply at 4°W → shallow shelf

So the shallowest point is 1755 m at 28°W, which is likely the crest of the Mid-Atlantic Ridge.

Then:
- To the west (48°W to 28°W): depth increases → moving away from ridge
- To the east (28°W to 10°W): depth increases → moving away from ridge

That makes sense!

And then at 4°W, depth drops to 145 m → continental shelf of Europe

So the Mid-Atlantic Ridge is at ~28°W, where depth is 1755 m, the shallowest point in the central Atlantic.

✔ So even though the overall depth is high, the ridge is the shallowest part.

Therefore, when plotting, you will see:
- Two deep basins on either side
- A central ridge at 28°W, 1755 m deep
- Then rapid shoaling to Europe at 4°W

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🎯 Final Answer: How to Chart the Ocean Floor

#### ✔ Steps to Solve the Problem:

1. Create a graph:
- X-axis: Longitude (°W), from 64 to 1
- Y-axis: Depth (m), from 0 to 5000 m
- Invert the y-axis so that deeper depths go downward (standard for bathymetric profiles)

2. Plot each point from the table.

3. Connect the points with a smooth line to create a cross-sectional profile.

4. Label features:
- Continental shelf at 64°W and 1°W (depth = 0 m)
- Abyssal plain (deep ocean) on both sides
- Mid-Atlantic Ridge at ~28°W, where depth is 1755 m (shallowest point in the central Atlantic)
- Steep slope from 5°W to 4°W (continental slope of Europe)

5. Conclusion:
- The Mid-Atlantic Ridge is a submarine mountain range formed by seafloor spreading.
- It is shallow compared to surrounding areas.
- This profile shows symmetrical deepening on both sides of the ridge.

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❗ Important Note:

There is a possible typo in the data:
- At 4°W, depth = 145 m
- At 5°W, depth = 4316 m

This implies a drop of over 4000 meters in just 1 degree of longitude (about 110 km), which is extremely steep but plausible for a continental slope.

So it's realistic — the European continental shelf drops off sharply.

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🧭 Summary

- The Mid-Atlantic Ridge is located near 28°W, where depth is 1755 m (shallowest point).
- The ocean floor deepens on both sides of the ridge.
- The profile shows a central ridge flanked by deep ocean basins.
- The sudden drop at 4°W indicates the continental shelf edge of Europe.

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✔ Final Task:

You should now:
1. Draw the graph.
2. Label the Mid-Atlantic Ridge at 28°W.
3. Label the continental shelves at both ends.
4. Describe how sonar works (as explained in the text).

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If you need help drawing the graph or interpreting specific points, let me know!