Correct Option
The correct option is 2 and 3 only.
Explanation
The gravitational force ($g$) on the Earth’s surface is not uniform. It is influenced by the Earth's shape (oblate spheroid), rotation, and the uneven distribution of mass within the Earth's interior. These variations serve as an indirect source of information about the Earth's internal structure.
Statement-wise Analysis
- Statement 1 is Incorrect: The gravitational force is not the same at all latitudes. It varies significantly depending on the location on the Earth's surface due to the planet's geoid shape and centrifugal force generated by rotation.
- Statement 2 is Correct: The Earth is flattened at the poles and bulges at the equator. Consequently, the distance from the Earth's center to the poles is less than the distance to the equator. Since gravitational force is inversely proportional to the square of the distance from the center ($g \propto 1/r^2$), the value of gravity is greater near the poles and lesser at the equator.
- Statement 3 is Correct: The gravity anomaly is defined as the difference between the observed value of gravity at a specific location and the expected (theoretical) value calculated assuming a uniform Earth. These anomalies indicate variations in the mass and density of materials within the Earth's crust and interior.
Key Takeaway
Key Takeaway: Gravity is strongest at the poles and weakest at the equator due to the Earth's oblate shape. Gravity anomalies reveal the uneven distribution of mass inside the Earth.