Iron is the ____most abundant element in the earth's crust.

Answer

To determine the abundance ranking of iron in the Earth's crust, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Most Abundant Elements**: Start by listing the most abundant elements in the Earth's crust. The top five are:
- Oxygen
- Silicon
- Aluminium
- Iron
- Calcium

2. **Rank the Elements**: Based on the list, assign ranks to each element:
- 1st: Oxygen
- 2nd: Silicon
- 3rd: Aluminium
- 4th: Iron
- 5th: Calcium

3. **Locate Iron's Rank**: From the ranking, identify the position of iron. It is the fourth element in the list.

4. **Conclude the Answer**: Therefore, iron is the fourth most abundant element in the Earth's crust.

### Final Answer:
Iron is the **fourth** most abundant element in the Earth's crust.

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