What the Rocks Say: Geology & Paleontology Flashcards
Describe how radioactive elements are used to determine the age of rocks.
The universe is full of naturally occurring radioactive elements. Radioactive atoms are inherently unstable; over time, radioactive “parent atoms” decay into stable “daughter atoms.”
When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. Afterwards, they decay at a predictable rate. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.
Define isochron and describe how they are used to date the age of rocks.
An isochron is a line on a
graph connecting points for
events that happened at the
same time. We the slope of an ischron to determine the age of rocks.
Describe how fossils are formed, what we can learn from them, and how they are dated.
Sedimeentary rocks are the richest source of fossils. Fossils are formed in many different ways, but most are formed when a living organism dies and is quickly buried by sediment. Soft tissues often decompose, leaving only the hard bones or shells behind. After the organism has been buried, more sediment, volcanic ash or lava can build up over the top of the buried organism and eventually all the layers harden into rock (they become ‘lithified’).
Discuss biomarkers and how are they used to learn about the history of life on earth.
A biomarker is molecular evidence of life in the fossil record. Biomarkers can include fragments of DNA, molecules such as amino acids, or isotopic ratios.
