The Earth's crust is primarily composed of eight major elements, not four. Here they are in order of abundance:

1. Oxygen (O): The most abundant element, making up about 46.6% of the Earth's crust.

2. Silicon (Si): The second most abundant element, accounting for about 27.7% of the crust.

3. Aluminum (Al): Makes up approximately 8.1% of the Earth's crust.

4. Iron (Fe): Found in a significant amount at 5.0% of the crust.

5. Calcium (Ca): Present at about 3.6% of the crust.

6. Sodium (Na): Makes up 2.8% of the Earth's crust.

7. Potassium (K): Found at about 2.6% of the crust.

8. Magnesium (Mg): Makes up about 2.1% of the Earth's crust.

While these elements make up the majority of the Earth's crust, other elements are also present in smaller amounts.