Soil Profile exercise - Free Printable

Let’s go step by step to match each soil horizon description with the correct letter from the key:

Key:
- E – eluviation layer
- C – parent rock
- B – subsoil
- A – topsoil
- R – bedrock
- O – organic layer

Now, let’s read each question and think about what it’s describing.

---

1. The ________ horizon is located above the bedrock and contains less humus, soluble minerals, and organic matter.

This sounds like the C horizon (parent rock) — it’s just below the B horizon and above bedrock. It has broken-up rock material but not much organic stuff.

→ Answer: C

---

2. The ________ horizon is mainly composed of organic materials such as dried leaves, grasses, small rocks, twigs, surface organisms and decomposed matter.

That’s the very top layer — dead stuff on the ground before it becomes soil. That’s the O horizon (organic layer).

→ Answer: O

---

3. The ________ horizon is also called the humus layer.

Humus = rich, dark, decayed organic matter mixed with soil. That’s the A horizon (topsoil) — where plants grow best.

→ Answer: A

---

4. The ________ horizon is composed of nutrients leached from the O and A.

Leaching means water carries things down. So this layer gets washed-out minerals from above — that’s the E horizon (eluviation layer).

→ Answer: E

---

5. The ________ horizon is very compact and is made of granite, basalt and limestone.

These are types of solid rock — so this must be the bottommost layer: R horizon (bedrock).

→ Answer: R

---

6. The ________ horizon is devoid of any organic matter and is made up of broken bedrock.

Broken bedrock? That’s still part of the parent material — but wait… actually, “broken bedrock” is often part of the C horizon, which is weathered rock above bedrock. But note: Question 1 already used C for “above bedrock, less humus”. Let’s double-check.

Actually, looking again — question 6 says “devoid of any organic matter and made up of broken bedrock” — that’s still C horizon. But we already used C in Q1.

Wait — maybe I misassigned Q1.

Let me re-read Q1: “located above the bedrock and contains less humus...” — yes, that’s C.

Q6: “devoid of any organic matter and made up of broken bedrock” — also C? That can’t be — each blank should have a different answer.

Hold on — perhaps Q6 is referring to R? No, R is unbroken bedrock.

Actually, standard soil profile:

From top to bottom:
O → A → E → B → C → R

So:

- O: organic litter
- A: topsoil (humus)
- E: leached layer
- B: subsoil (accumulates clay/minerals)
- C: partially weathered parent rock
- R: solid bedrock

Now, Q6: “devoid of any organic matter and made up of broken bedrock” — that’s C horizon.

But Q1 also said “above bedrock, less humus...” — also C?

Hmm — maybe Q1 is actually describing B horizon?

Let’s check Q1 again: “located above the bedrock and contains less humus, soluble minerals, and organic matter.”

Actually, B horizon (subsoil) is below A and E, above C. It has some minerals leached down, but less organic matter than A.

And C horizon is even lower — mostly broken rock.

Perhaps Q1 is B? Let’s see other clues.

Look at Q7: “The soil profile extends from the ________ surface to the rock material.”

That’s likely O — because soil starts at the organic layer on top.

But let’s list all questions again with better matching.

Standard definitions:

- O: Organic layer — dead leaves, etc.
- A: Topsoil — humus, roots, organisms
- E: Eluviation — leached out, pale color
- B: Subsoil — accumulates clay, iron, aluminum; less organic
- C: Parent material — broken rock, little organic
- R: Bedrock — solid rock

Now match:

Q1: “above bedrock, less humus, soluble minerals, organic matter” → This fits C (parent rock) — it’s directly above R, and has minimal organics.

Q2: organic materials → O

Q3: humus layer → A

Q4: nutrients leached from O and A → E

Q5: compact, granite/basalt/limestone → R (bedrock)

Q6: devoid of organic matter, broken bedrock → C? But we already used C in Q1.

Wait — maybe Q1 is B?

Let’s read Q1 carefully: “located above the bedrock” — if bedrock is R, then above it is C, then B.

“Contains less humus, soluble minerals, and organic matter” — compared to what? Probably compared to A or O.

Actually, B horizon has less organic matter than A, and may have accumulated some minerals.

But “soluble minerals” — those are usually leached *out* of E and deposited in B.

I think there’s confusion.

Let me look at typical textbook descriptions:

- B horizon (subsoil): accumulation of clay, iron, aluminum; less organic matter; below A/E
- C horizon: weathered parent material; no biological activity; above bedrock
- R horizon: unweathered bedrock

So for Q1: “located above the bedrock” — could be C or B.

But “contains less humus, soluble minerals, and organic matter” — if it’s comparing to upper layers, both B and C fit, but C has almost none.

Perhaps Q1 is C, and Q6 is also C? That can’t be.

Wait — Q6 says: “devoid of any organic matter and is made up of broken bedrock” — that’s definitely C.

Then Q1 must be something else.

Let’s read Q1 again: “The ________ horizon is located above the bedrock and contains less humus, soluble minerals, and organic matter.”

Maybe it’s B? Because B is above C and R, and has less organic matter than A.

In many profiles, B is described as having reduced organic content.

Also, “soluble minerals” — in B, you find accumulated minerals that were leached from above.

Whereas C has mostly inert rock fragments.

So perhaps:

Q1: B (subsoil) — located above bedrock (well, above C and R), has less humus than A, and has some soluble minerals that accumulated.

Q6: C — broken bedrock, no organic matter.

Yes, that makes sense.

Let’s confirm with other questions.

Q4: “composed of nutrients leached from O and A” — that’s E — eluviation layer, where things are washed out.

Q5: compact, granite etc. — R

Q2: organic materials — O

Q3: humus layer — A

Q7: “extends from the ________ surface to the rock material” — soil profile starts at the top, which is O layer.

So now:

1. B
2. O
3. A
4. E
5. R
6. C
7. O? Wait, Q7 says “from the ________ surface” — probably “organic” or “O”, but let’s see.

Q7: “The soil profile extends from the ________ surface to the rock material.”

Typically, we say from the surface (which is O horizon) down to bedrock.

So “O” or “organic” — but the blank is for the letter name.

Looking back at the key, it’s letters: E, C, B, A, R, O.

So Q7: from the O surface? Or perhaps they mean the top layer.

Actually, in some contexts, the soil profile starts at the mineral surface, but usually includes O.

Given that Q2 and Q3 refer to O and A, and Q7 says “surface”, it’s likely O.

But let’s list all answers:

After careful thought:

1. The B horizon is located above the bedrock (actually above C and R) and contains less humus... — yes, subsoil has less organic matter.

2. O — organic materials

3. A — humus layer

4. E — leached nutrients

5. R — bedrock, compact rock

6. C — broken bedrock, no organic matter

7. O — from the organic surface down to rock

But Q7 says “the ________ surface” — and in soil science, the “surface” might refer to the top of the mineral soil, but given the context, and since O is listed, it’s probably O.

However, let’s check if there’s a standard phrase.

Actually, upon second thought, the soil profile typically extends from the surface (which includes O) to bedrock. So “O” is correct.

But in some definitions, the profile starts at the A horizon, but here O is included.

Given the options, and that Q2 describes O as organic materials, Q7 likely refers to O.

Now, to confirm Q1: Is B really “located above the bedrock”? Well, technically, B is above C, which is above R. So indirectly yes.

And “contains less humus, soluble minerals, and organic matter” — compared to A, yes, B has less humus and organic matter, and may have soluble minerals that accumulated.

Whereas C has almost no soluble minerals — just rock fragments.

So Q1: B

Q6: C

Yes.

Final mapping:

1. B
2. O
3. A
4. E
5. R
6. C
7. O

But Q7: “from the ________ surface” — if it’s “O surface”, that might be redundant, but it’s acceptable.

Perhaps they mean the top layer, which is O.

Another way: sometimes “surface” refers to the ground surface, which is O horizon.

So I think it’s correct.

Let’s write the answers:

1. B
2. O
3. A
4. E
5. R
6. C
7. O

But wait — in Q7, it says “to the rock material” — which is R, so from O to R.

Yes.

Now, to box the final answer as per instruction.

Since the user wants the answers filled in, I’ll list them in order.

Final Answer:
1. B
2. O
3. A
4. E
5. R
6. C
7. O