{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture8 - Geologic deformation EARTHQUAKES pattern...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Geologic deformation Geologic structures: dynamically-produced patterns or arrangements of rock or sediment that result from tectonic forces within the Earth • produced as rocks change shape , location & orientation in response to applied stress structural geology is the study of the shapes, arrangement, and interrelationships of bedrock units and the forces that cause them • "forces"? - that which change motion or orientation of a body - EARTHQUAKES pattern recognition could be bedrock/tectonic plate
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 Stress is a force per unit area • three basic types of stress (in geology) 1) compressional – shortens 2) tensional – elongates 3) shear – parallel slippage • rocks subjected to stresses greater than their own strength begin to deform • continuum of folding / flowing or fracturing / rupture compression tension shear depend on rates - slow rate - flow - fast - breakage or rupture slippage along discrete planes on a rock body
Background image of page 2
3 Rocks can behave 3 ways: 1) if deformed materials return to original shape after stress removal, they are behaving elastically • however, once the stress exceeds the elastic limit of a rock, it deforms permanently 2) ductile deformation involves bending plastically 3) brittle deformation involves fracturing/rupture ..rubber band • if stress results in irreversible changes in shape or size of rock… • strain is a change in size or shape in response to stress stress is the applied force • strain is the deformation brittle ductile - essentially where we get earthquakes 1) - after earthquake - small earthquakes - relaxation of the rest of the rock body - trying to return to original shape - malleable rock has shattered and broken change of shape
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
4 • amount & rate stress Low strain rate promotes ductile deformation • type of rock Mechanically weak rocks tend to deformation through ductile processes • temperature & (confining) pressure High T promote ductile deformation High confining P promotes ductile deformation ..glass window ..shale ..migmatite Rocks behave as elastic , ductile or brittle depending on: Folds wave-like undulations in rock layers • mm-km scale features • result from horizontal or lateral compressional forces • described by the orientation of axial plane Ductile deformation (flow) & folding rapid strain - things fracture and break - bottom of the rock cycle, high confining pressure and temp COMPRESSIONAL FORCES! axis of the fold
Background image of page 4
5 Ductile deformation (flow) & folding shape of A also defined by axial plane - axial plane - where most curvature occurs km-scale folding
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
6
Background image of page 6
7 A series of anticlines & synclines axial plane has a bit of a plunge to it, like an arrow pointing into the ground
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
8 dome • upwarped displacement of rocks basin • downwarped displacement of rocks circular or slightly elongated structures - interference of folds interference of synclines basin
Background image of page 8
9 Brittle deformation (rupture) & faulting • loss of cohesion of a body under the influence of deforming stress • usually occurs along sub-planar surfaces that separate zones of
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}