Key Idea.
Section 1
Sediment Builds Rock Layers
The formation of sedimentary rock follows a strict physical sequence. Sediment settles on the ground or sea floor due to gravity, forming a horizontal layer.
Over time, as environmental conditions continue, new sediment is deposited. This process results in the accumulation of multiple rock layers stacked on top of one another.
Section 2
Rock Layers Reveal Relative Age
Because new sediment always settles on top of existing sediment, a vertical stack of rock layers acts as a timeline. The layer at the very bottom had to be there first to support the others, making it the oldest. The layer at the very top was deposited last, making it the youngest.
This scientific rule, known as the Principle of Superposition, allows geologists to determine the relative age of rocks and the fossils contained within them.
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Section 1
Sediment Builds Rock Layers
The formation of sedimentary rock follows a strict physical sequence. Sediment settles on the ground or sea floor due to gravity, forming a horizontal layer.
Over time, as environmental conditions continue, new sediment is deposited. This process results in the accumulation of multiple rock layers stacked on top of one another.
Section 2
Rock Layers Reveal Relative Age
Because new sediment always settles on top of existing sediment, a vertical stack of rock layers acts as a timeline. The layer at the very bottom had to be there first to support the others, making it the oldest. The layer at the very top was deposited last, making it the youngest.
This scientific rule, known as the Principle of Superposition, allows geologists to determine the relative age of rocks and the fossils contained within them.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter