Because the oldest parts reach the continental crust and then the ocean floor sinks beneath the continental crust, into the mantle.
Where DID trilobites live? In the ocean, between 530 million and 250 million years ago.
We evolved about 500 million years ago from fish that evolved to anphibians then mammals then we evolved to primates
Samples of sea floor basalt reveals that they do not exceed 200 million years of age. With the oldest continental rocks being in the neighborhood of 4 billion years of age, there's obviously some crust creation and destruction going on. Samples also indicate changing magnetic orientation in the magnetic minerals present in the basalt, with a matching orientation on the opposite side of the divergent boundary. This indicates that crust is being formed simultaneously on both sides of the mid-ocean ridge, over time, with the magnetic orientation matching the existing orientation at the time of its formation.
The oldest indications of the existence of real land plants have been found in cores from boreholes in Oman. The plant fossils have been found in the middle Ordovician and are about 475 million years old.
The math is fairly simple. Simply multiply the rate of 2.5cm/year by 200 million years and you get an answer of 500 million centimeters. To put it in more familiar units the ocean basin is 5,000 kilometers wide.
Because the oldest parts reach the continental crust and then the ocean floor sinks beneath the continental crust, into the mantle.
The oldest oceanic crust is in the west Pacific and north-west Atlantic. They are about 180 to 200 million years old.
The oldest continental crust would be between three and one half to four billion years older than the oldest oceanic crust. This is due to the fact that ocean plates are subducted under the continental plates, subjected to partial melt and essentially recycled in the mantle before reforming.
The oldest continental crust would be between three and one half to four billion years older than the oldest oceanic crust. This is due to the fact that ocean plates are subducted under the continental plates, subjected to partial melt and essentially recycled in the mantle before reforming.
The oldest ocean, geologically, is the Panthalassa Ocean which was around 220 million years ago in the Triassic era. It encompassed the whole Earth except the land mass Pangea. See related link for more information.
Rocks in ocean crust are generally as old as 200 million years. The oldest oceanic crust is found near continents, which can be around 250 million years old. However, most of the oceanic crust is continually being formed and destroyed through seafloor spreading and subduction, so rocks are often much younger.
200 million
200 million
On average, continents are older than ocean basins. Due to the action of plate tectonics, ocean crust is being formed and destroyed continuously. The oldest oceanic crust is about 200 million years old, whereas continents, which are less dense than oceanic crust and tend not to be subducted into the mantle, can be more than 3,000 million years old in places.
The oldest continental crust would be between three and one half to four billion years older than the oldest oceanic crust. This is due to the fact that ocean plates are subducted under the continental plates, subjected to partial melt and essentially recycled in the mantle before reforming.
200 million.
It varies, but the oldest part is 180 million years old