The oldest rocks known on Earth formed about 4.0 billion years ago--we think that the Earth had a solid surface, and even oceans, earlier than that, but active geological processes like erosion and plate tectonics have removed all the older rocks.
(The oldest rocks; known; L:on Earth) (even oceans, earlier than that, but active geological processes like erosion and plate tectonics; have removed; all the older rocks) (we; think; that the Earth had a solid surface, and even oceans, earlier than that, but active geological processes like erosion and plate tectonics have removed all the older rocks) Context(we think,List([68, 76))):(The oldest rocks known on Earth; formed; T:about 4.0 billion years ago) Context(we think,List([68, 76))):(the Earth; had; a solid surface)
we think,List([68, 76)) we think,List([68, 76))
The oldest rocks even oceans, earlier than that, but active geological processes like erosion and plate tectonics we The oldest rocks known on Earth the Earth
known have removed think formed had
L:on Earth
all the older rocks
that the Earth had a solid surface, and even oceans, earlier than that, but active geological processes like erosion and plate tectonics have removed all the older rocks
T:about 4.0 billion years ago
a solid surface