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at ridges
what do Plate motions do
Put stress on boundaries and existing faults.
Elastic Deformation
Rocks and faults deform elastically in response to building stress.
what is Strain
The change in shape of rock due to stress.
how does an earthquake occur
Occurs when stress exceeds the ability of rocks to lock faults.
Focus
The original starting point of an earthquake.
Brittle Deformation
Deformation that causes rocks to break.
Ductile Deformation
Deformation that allows rocks to bend without breaking.
Normal Fault
A fault where the footwall moves up due to tensional stress.
Reverse Fault
A fault where the footwall moves down due to compressional stress.
Thrust Fault
Similar to a reverse fault but with a shallower angle relative to Earth's surface.
Synclines
Rock strata that dip towards the hinge of a fold.
Axial Plane
An imaginary plane that contains the successive hinges of a fold.
Geological Structures
Configurations formed in rocks due to tectonic forces.
Uniformitarianism
The principle that Earth processes we observe today occured in the past and are recorded in rocks.
Numerical Age
The quantifiable age of a rock or fossil.
Relative Age
The age of rocks or fossils in comparison to others.
Superposition Principle
In undisturbed sedimentary rocks, the oldest layer is at the bottom.
Lateral Continuity
Sedimentary layers extend in all directions until they thin out.
Cross-Cutting Relationships
Rocks that cut across other rocks are younger than the rocks they cut.
Anthropocene
A proposed new geological epoch characterized by significant human impact on Earth's geology.
Erratics
Boulder-sized foreign rocks transported by glaciers.
Kettle Lakes
Small, roughly circular lakes formed by glaciers.
Moraines
Narrow hills composed of unsorted sediments left by glaciers.
Horn
Mountain peaks eroded by glacier action, representing local maximum elevation.
Arete
Ridges that separate glaciated valleys.
Cirque
Bowl-shaped valleys formed by glacial erosion.
Rock Flour
A fine powder created by a glacier as it scrapes over bedrock.
Ductile Structures
Structures formed when rocks bend rather than break.
Sedimentary Basin
Low-lying areas where sediment accumulates, often adjacent to mountain ranges.
Basins
Areas where younger rock is found at the hinge in geological folds.
Where is the thickest lithosphere
at mountains
where does ductile deformation take place
in the asthenosphere
where does brittle deformation take place?
in the lithosphere
in a dome, where are the oldest rocks located?
at the center of the dome in the hinge
in a basin, where are the oldest rocks located?
at the edges of the basin
tools to infer relative age
Original horizontality, Superposition, Lateral continuity, Cross Cutting
What is a Glacier?
A large mass of ice that moves slowly over land, formed from compacted snow.
What is glacial retreat?
The backward movement of the glacier front due to melting or loss of ice.
What is glacial till?
Unsorted sediment deposited directly by glacial ice as it melts.
how can you tell the difference between a valley carved by water vs. a valley carved by a glacier.
Glaciers have steeper sides and a U-shaped profile, while water-carved valleys tend to have a V-shaped profile and gentler slopes.
how do glaciers transport erratics?
weather erodes boulder from bedrock, allowing the glacier to pick it up and transport it as it moves equator-ward. when glacier retreats, it move back pole-ward, depositing the boulder.
