The Earth is not exactly oval in shape; it is more accurately described as an oblate spheroid. An oblate spheroid is a sphere that is slightly flattened at the poles and bulges at the equator. This shape is a result of Earth's rotation.
The Earth's rotation causes a centrifugal force that acts perpendicular to the axis of rotation. This force effectively pushes material away from the axis, resulting in a bulge around the equator. At the same time, the force of gravity pulls material towards the center of mass, trying to make the Earth spherical. These two forces, gravity and centrifugal force, reach a balance that leads to the oblate spheroid shape.
Additionally, factors such as the Earth's rotation speed, its composition, and the distribution of landmasses and oceans also influence its shape. These factors can cause slight irregularities, resulting in local variations in the Earth's shape, such as mountains and ocean trenches.
It's important to note that the Earth's shape is not perfectly smooth or uniform. It has mountains, valleys, and other topographical features that create variations in gravitational pull across the surface. This irregular distribution of mass contributes to the complex and dynamic nature of our planet.