Earthquake Notes Crustal Deformation

REVIEW: So far we have found that convection currents cause several things to happen. 1. Continental movements 2. Earthquakes 3. Volcanoes 4. Mountains

ISOSTATIC ADJUSTMENT up and down movements of crust. This adjusts for uplift and weathering of mountains. These movements cause…

STRESS ON THE ROCKS!!!! Stress - the amount of force placed on the rocks, also called STRAIN. There are 3 TYPES OF STRESS

COMPRESSION Pushing together of rocks TENSION Pulling apart of rocks SHEARING Lateral (side to side) tearing of rocks With Continental Movements comes breaks and folds in the rocks of the continents.

3 TYPES OF FOLDS Limbs - sides of the fold or rock layers before and following a fold. ANTICLINE - an upward fold in rock layers where oldest rock layer is in the center of the fold. Limbs fold down, it forms a ridge (hill)

3 TYPES OF FOLDS 2. SYNCLINE_ a syncline is a downward fold in the rock layers where youngest rocks are in the center. Limbs fold up, it forms a valley.

3 TYPES OF FOLDS 3. MONOCLINE_ slight fold in one area but both limbs remain horizontal 4. Dip (steepness) of the limbs reflects the intensity of the fold. 5. Strike is the compass direction of the fold of the rock layer. 6. Folding can be so severe the rock layers are overturned or upside down.

2 TYPES OF BREAKS IN ROCK LAYERS: FRACTURE_ Break in rock layers where no movement has occurred. FAULT_ Break in rock layers where movement has occurred or is currently happening. There are several in Kentucky Movements along faults account for 80% of all earthquakes, the other 20% from plate boundaries.

2 SIDES TO EVERY FAULT: Look at it this way, imagine you are standing on a fault: HANGING WALL- surface of rock directly above the fault plane. (over your head) FOOTWALL- surface of rock directly below the fault plane. (your are feet on it) UNC geologists illustrating the concept of footwall and hanging wall at a small fault near Las Vegas, Nevada. Their feet are on the footwall, and the hanging wall is hanging over their heads. This is a small normal fault. Grooves and scratches on the fault plane run down the dip of the plane.

MAJOR TYPES OF FAULTS NORMAL FAULT- occurs when hanging wall moves down. You think it is NORMAL because gravity would act on it so it drops down This is caused by a Tension force on this type of fault. Convections cells pulling on rocks of crust cause tension force.

MAJOR TYPES OF FAULTS REVERSE FAULT- hanging wall moves up due to compression forces, this moves opposite of the normal fault. Convections cells pushing on rocks of crust cause the compression force.

MAJOR TYPES OF FAULTS THRUST FAULT- Special kind of reverse fault, the angle of the fault plane is very low, almost horizontal. STRIKE-SLIP FAULT -( Transform fault) The rocks move horizontally in relation to each other by Most common at transform boundaries like: San Andreas Fault in California.

MOUNTAINS FORM IN 3 WAYS CONTINENTAL VS OCEANIC PLATES_ Produces much crustal deformation. High mountains produced, mostly volcanic because the ocean plate is subducted beneath the continent. Ex Cascade Range.

MOUNTAINS FORM IN 3 WAYS OCEANIC VS OCEANIC_ Produces little crustal deformation. Large volcanic mountain islands form. Peaks of these volcanic mountains reach from ocean floor to surface. Ex. Mariana Islands in North Pacific form.

MOUNTAINS FORM IN 3 WAYS CONTINENTAL VS CONTINENTAL_ Produces intense crustal deformation with immense mountain ranges of folded and faulted mountains. Ex Himalayas.

4 KINDS OF MOUNTAINS FOLDED_ Highest mountains in the world, rocks squeezed together like an accordion. Ex. Appalachian PLATEAU_ Large areas of flat-topped rocks high above sea level. Formed by thick horizontal layers of rock slowly uplifted. Most are next to mountain ranges. Ex. Tibetan Plateau

4 KINDS OF MOUNTAINS FAULT-BLOCK MOUNTAINS_ Sections of crust broken into large blocks and shifted, up, down, or over other sections. Ex Nevada, Arizona, Utah… GRABENS_ These develop when steep faults break crust into blocks, then block(s) slips downward along normal faults. Ex Death Valley Ca.

4 KINDS OF MOUNTAINS VOLCANIC_ Molten rock erupts onto surface, on land, ocean floor. Some of largest are along mid-ocean ridges. Others over hot spots. Ex Azores and Hawaiian islands. DOME_ Unusual, molten rock rises through crust, pushes up rock layers, never melts through to surface. Eventually, cools and hardens, erosion removes rocks over it leaving separate high peaks. Ex Black Hills of South Dakota, Adirondack Mountains of New York State.

Strike-slip fault The rocky blocks on either side of strike-slip faults, scrape along side-by-side, no vertical movement means no hanging or foot wall.

Thrust fault along Interstate-70, Silverthorne --- Younger rocks on the very bottom of this picture have been thrust under older rocks and pushed west (left) for several miles. The fault line ascends slowly from the lower right edge of the picture to beyond the center where some folding of the layers at the fault contact can be seen.

Reverse Fault Along a reverse fault one rocky block, the hanging wall, is pushed up relative to rock on the other side.

Normal Fault A normal fault drops rock on one side of the fault down relative to the other side. Take a look at the side that shows the fault and arrows indicating movement

Fracture Note the number of fractures these are small others can be huge.

Huge faults visible in the side of this canyon Huge faults visible in the side of this canyon. This faulting occurred over 20,000,000 years. This is what faulting can do to the surface of the earth during an earthquake. This faulting occurred during 1 earthquake.

Known Major KY Faults FIGURE 16.--. Solid lines indicate fault traces.

Tension VS undeformed rock strata Back to Normal

Shearing VS undeformed rock strata

Compression verses undeformed rock strata

This Anticline is 500 feet thick.

This Syncline is 4000 ft tall

This Monocline is barely 5 feet thick.