Earth Formed
Earth was formed 4.6 billion years ago. scientist believe that Earth began of a ball of ice dust and rock, then as gravity increased all the ice dust and rock got pulled together.
Oceans Formed
About four BYA (billion years ago) the water was too hot to stay in liquid form. Then as Earths surface cooled the water vapor turned into rain. It rained for a really long time then the oceans started to form.
Oldest Rock
Earth is continuously recycling old crust and replacing it with new crust so it is very hard to find acient rock because they are uncommon. The oldest rock is in Canada and was formed about 3.8 BYA.