Presentation on theme: "RELATIVE TIME: When the age of rock is compared to the ages of other rocks or events in geological time. Can determine which layers are older than others."— Presentation transcript:
RELATIVE TIME: When the age of rock is compared to the ages of other rocks or events in geological time. Can determine which layers are older than others to define the sequence of events on Earth. ABSOLUTE TIME: Identifies the exact date of an event. Ex: 65 Million Years Ago
PRINCIPLE OF UNIFORMITARIANISM All the geological processes (weathering, erosion, volcanism, earthquakes, etc.) that occur today also occurred in the past in the same ways. “The Present is the Key to the Past”
PRINCIPLE OF ORIGINAL HORIZONTALITY Sediments are deposited in flat lying or horizontal layers. If rocks are tilted or folded, they have been deformed after deposition.
PRINCIPLE OF SUPERPOSITION States that the rock layers on the bottom are oldest, the rock layers on the top are youngest. Unless the rock layers are overturned or folded
PRINCIPLE OF CROSS-CUTTING RELATIONSHIPS If something cuts through rock layers, the rock layers must be older than the thing cutting through them.
IGNEOUS INTRUSION When magma breaks through the rock layers and cools into an igneous rock
CONTACT METAMORPHISM When magma “scars” and heats up existing rock layers. This alters the rock into metamorphic rock.
IGNEOUS EXTRUSION When magma reaches the earth’s surface and cools into igneous rock.
IGNEOUS EXTRUSION How do we know this is an extrusion? Because there is no contact metamorphism on the top of the layer of igneous rock!
FOLD: Permanent bend or curve FAULT: Bend in the earth’s crust
UNCONFORMITY A break/gap in the rock record Represented by a wavy line The gap represents an unknown length of time. Rocks above are younger. Rocks below are older.