Fact 1: Being burried under soil and mud changes vegetation into peat through extreme heat and pressure in a swamp over a long period of time.

Fact 2: Wetlands Wetlands are also called swamps or marshes.

Given the two facts above, answer the question "Buried vegetation in a wetland changes to peat over what?" with the following options: 
- a long period of time
 - The area was once underwater
 - a brief period of time
 - just a day's time
 - Physical weathering
 - It used to be covered by water
 - movements in the earth's crust
 - a quick period of time


 

 a long period of time        