The Three Principles of Geology Lecture Notes – Key Impact Craters Ejecta Material

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The Three Principles of Geology Lecture Notes – Key
Impact Craters
1. Ejecta – Material from the crater that was thrown high into the air and landed
outside the crater in a blanket.
2. Rim – The raised area round the edge of the crater.
3. Peak – An impact violent enough to melt the rock which formed a central uplift.
4. Walls – The crater slope down to the floor.
5. Floor – The bottom of the crater; it is usually flat.
Identify the parts of the crater.
Central Peak
1. Lava – Hot, molten rock.
2. Vent – Cracks in the planet’s crust.
3. Caldera – A roughly circular depression found at the top of the volcano.
4. Shield Volcano – Domes much wider than they are high (shaped like a
Shield) and have very low slopes.
Stratification – Layers of rock that are laid on top of the previous layer.
River Beds – Long, snake-like formations that resemble dry river beds similar to
those found on Earth.
The Three Principles
The Principle of Superposition
Strata located at the bottom of an undisturbed stack of rocks are older than the
layers at the top of the stack.
The Principle of Cross-Cutting Relationships
Rocks or geological features such as canyons, river, or cracks in rocks may be cut
by other rocks or by other geological features.
The Principles of Horizontal Bedding
If the layers are no longer horizontal they must have
Been bent or folded after they were originally laid down.