Scientists determine that the rocks in the ash layer are 200 million years old. Several types of fossil organisms can be found below the ash layer but not above it.
What is the most reasonable conclusion from this information?
(Will give extra points)

Amath expression is a collection of one or more terms, which are separated by the signs ( + , - , x , / ).example :   8+b8+b  or  a−3a−3in algebra, an equation is a mathematical statement with two expressions where, each expression is separated by an equal (=) sign. variables can be present on both the sides of the equality (=) sign and we use letters to denote such variables.example 1:   x=4+2x=4+2  , [here, we can observe that the variable is present only on one side of the equation].example 2:   2x+3=x+42x+3=x+4  , [here, we can observe that the variables are present on both side of the equation].

i didn’t understand your question but archipelagos are groups of island hope this

The answer is a for sure