Determining Relative Age Chapter 8 - 1 Determining Relative Age

Age of the Earth 4.6 billion years old James Hutton was 1st to determine this Scottish physician and farmer

Uniformitarianism Same forces that change the Earth today changed it years ago Present is the key to the past

Rate of processes may change

Earth’s Age Before Hutton most believed Earth was 6,000 years old Many believed that all features formed at the same time

Processes that change the Earth today are very slow Millions of years would have to have passes to get what we have today

Relative Age Layers of rock show events Indicates that one layer of rock is older than another Nothing about age

Law of Superposition A layer of sedimentary rock is older than the layer above it It is younger than the layer below it

Principle of Original Horizontality Rock generally forms in horizontal layers Unless disturbed

Rocks that are not horizontal have been tilted or deformed Sedimentary rocks

Graded Bedding Larger particles should be at the bottom of the rock layer

Cross - Beds Sandy sediments formed curved beds Tops of layers erode before new form Curved at bottom and cut off at top

Ripple Marks Crests of ripple marks point up

Unconformities A break in the geologist record Missing parts

Nonconformity Stratified rock rests on unstratified rock

Angular Conformity Layers are tilted

Disconformity Boundary between order and newer layer is missing

Crosscutting Relationships Fault or igneous intrusion are older than the rock it cut through