What is rock strata? Strata- plural form of stratum Stratum-  a layer or a series of layers of rock in the ground.

Determining Geological Ages Relative Age Dating – placing rocks and geologic events in their proper sequence Absolute Age Dating – define the actual age of a particular geologic event

What is cross-cutting?

Sometimes magma pushes, or intrudes, into cracks in existing rocks Sometimes magma pushes, or intrudes, into cracks in existing rocks. When the melted rock cools and solidifies, the resulting feature is called an igneous intrusion.  The principle of cross-cutting relationships states that an igneous intrusion is always younger than the rock it cuts across.

How Impression Fossils Form Cast forms when mold is filled in with mineral water 1. Shells settle on ocean floor Rock broken to reveal fossil cast Rock broken to reveal external mold of shell 2. Shells buried in sediment 3. Mold, or cavity, forms when original shell material is dissolved

Metamorphic Rock- formed when rocks are changed by heat and pressure   Types of Rocks Sedimentary Rock- formed when sediments are pressed & cemented together Metamorphic Rock- formed when rocks are changed by heat and pressure Igneous Rock- formed from melted rock that has cooled and solidified. 

Weathering and Erosion Erosion- when rock fragments are moved by some force of nature Weathering- when rocks are broken down into smaller fragments Deposition - when rock fragments are laid down in a new location