Since its formation the Earth has had a tilted axis of rotation as compared to its plane of orbit. The tilt is currently 23.5 degrees but varies between 22.1 and 24.5 degrees in a cycle that averages about 40,000 years to complete. Earth's tilt is currently increasing towards the 24.5 degree limit.
It is the result of how the earth was formed.
Earths tilt
Depending on the position of earth in its orbit and which hemisphere is closer to the sun due to the Earth's tilt on its axis, different seasons are the result.
The Earth's tilt is what causes the seasons.
Earth's axial tilt is 23.44°.
23.5 degrees
The earths tilt at its axis
Seasons
mostly climate
23.5 degrees
No. Erosion could not have such a dramatic effect on Earth's rotation. The tilt on Earth's axis is likely a result of a collision with another planet early in Earth's history. This same collision formed the moon.
Earth's tilt is much older than that - it probably had its tilt for millions of years.