Final answer:
Earth is believed to have formed about 4.5 to 4.6 billion years ago, with the oldest rocks, indicative of early stable land masses, dating back to about 3.5 billion years ago according to uranium-238 dating.
Step-by-step explanation:
The Earth formed about 4.5 to 4.6 billion years ago. Initially, it was a molten mass with no atmosphere or oceans. Over time, the atmosphere developed, and as the Earth's surface cooled, the first stable land masses began to form.
According to radioactive dating, specifically uranium-238 dating, the oldest rocks on Earth solidified around 3.5 billion years ago. This would indicate that the Earth's surface had cooled enough for the first stable land masses to form by this time. Alongside this geological evidence, the formation of the first oceans and atmosphere marked the planet's progression towards sustaining life.