post exam 2 geo content

1. how many people do mass movements kill in the US every year? 

1. 25-50

1. how many people do mass movements kill every year worldwide? 

thousands

1. where do mass movements occur? 

1. anywhere there is elevated terrain

1. why do mass movements kill a lot of people in the Asia area? 

1. a lot of tectonic activity → earthquakes

2. Indonesia has the most volcanoes in the world, which cause lahars, falling under the category of mass wasting

3. topography → a lot of mountains and slopes

4. socioeconomic status → more developing nations, more people die there

5. topical area, lots of precipitation which drives mass movements

6. population density

1. how much money have mass movements caused annually in the US since 1980?

1. $2-4 billion dollars 

1. economic results of mass movements: 

1. decrease real estate and tourism revenue

2. decrease productivity - if you have to go into work, that can cause a serious problem → can increase commute time or prohibit you from going to work at all

1. high potential areas for landslides in the US and why?

1. around mountainous areas – Appalachia is more hazardous than the Rockies, because they have a lot more precipitation than the Rockies and higher population in the Appalachians than the west

2. Mississippi River → flood areas

1. what are the four primary classes of mass movements? 

1. falls & topples

2. slides

3. flows

4. lateral spreads

1. what are falls and topples?

1. the materials lose contact with the ground and move through the air

1. what are slides? 

1. materials slide or glide along a zone of weakness separating it from the stable underlying material

2. can move as a whole unit or separate

1. what are flows? 

1. materials lose internal cohesion and move as a fluid

1. what trigger flows and vice versa? 

1. flood events can trigger flows

2. flows can cause flood events

1. what are lateral spreads? 

1. flat or gently sloped areas that move as a result of shear / tensile fractures 

1. what are mass movements subdivided based on? 

1. type of material involved (predominantly rocks vs. soils / sediments)

2. curvature of the land rupture (slides)

3. speed of movement or the percentage of water present (flows)

1. difference between translational and rotational slide: 

1. translational → planar movement

2. rotational → curved

1. how do the materials in a geographic location impact the type of movement that would be present? 

1. materials like unconsolidated sediments, especially clay and shale, are prone to rapid flows

2. strong, resistant rocks are less susceptible to mass movement, but can still be prone to falls or slides if fractures or weakness are present

1. what is bedrock? 

1. solid rock connected to the ground

1. what is debris? 

1. unconsolidated material that can be rock fragments, sand, silt, mud, or mixtures thereof

1. what is soil? 

1. mixture of weathered rocks and organic material

1. what can the character of a rupture be? 

1. curved and rotational (slumps) 

2. planar / translational

1. what is the strength of a slope called? 

1. shear strength

1. when will a slope fail in relation to shear strength? 

1. When the force trying to move it (shear stress) becomes equal to or greater than that strength, the slope will collapse.

1. factors that influence the shear strength: 

1. slope

2. material

3. climate

4. tectonics

5. triggering mechanisms

1. what is angle of repose? 

1. slope of material before it can go no steeper because gravity drags it down

1. impact of a little water on angle of repose: 

1. having a little water is good because it acts to increase the surface tension

1. impact of too much water on angle of repose: 

1. too much water causes material to behave more like a fluid

2. water adds weight, can cause shrinkage / swellage of some clay minerals, decreasing clay binding

1. how does vegetation contribute to slopes? 

1. vegetation works to stabilize slopes by holding the land surface together, absorb water, and reducing erosion and over-steepening

1. what do human attempts to change slopes do? 

1. disrupt the natural balance and stability of the soil or rock, affecting the angle of repose 

1. MAIN CAUSE of landslides: 

1. precipitation

1. SECOND MAIN CAUSE of landslides: 

1. earthquakes, especially large numbers of them 

1. what do landslide hazards and predictions revolve around?

1. identifying old mass movements

1. what should you look for in an area to determine landslide hazards and predictions:

1. previous landslides

2. tilted cultural features and vegetation

3. irregular soil pattern

4. overgrown loose material

5. hummocky ground surfaces

6. back tilted blocks

7. arcuate scarps

1. what are hummocky ground surfaces?

1. uneven, irregular landscapes characterized by small hills (hummocks) and depressions

1. what are back tilted blocks?

large sections of rock or earth that have rotated backward (upslope) relative to the direction of movement, typically during a landslide

1. what are arcuate scarps?

1. curved, steep cliff-like features that form at the head (top) of a rotational landslide

1. what factors should landslide hazard assessment be based on?

1. previous landslides

2. rock types and their distribution

3. rock strength

4. slope

5. precipitation

1. what does structural geology deal with? 

1. orientation of rock units beneath surface

2. deformations of rocks that may have taken place

3. stresses that cause deformation

4. deducing the processes that caused the stresses and deformation

1. how to calculate pressure:

1. density x gravitational constant x depth

1. what is the pressure in the Earth due to?

1. hydrostatic pressure and lithostatic pressure

1. what is hydrostatic pressure?

1. pressure exerted by a water due to gravity

1. what is lithostatic pressure?

1. pressure exerted on a rock by the weight of overlying rocks

1. relationship between hydrostatic and lithostatic pressure:

1. both increase with depth, but lithostatic pressure is always greater than hydrostatic pressure at the same depth

1. how is stress measured?

1. force per area - bars, atm

1. what are the three types of stress?

1. compressive 

2. tensional 

3. shearing

1. show the three types of forces acting on an imaginary object with fingers

1. what is strain? 

1. deformation

2. response of a rock due to imposed stress, typically a change of shape

1. what kind of stress occurs at divergent plate boundaries / mid ocean ridges?

tension

1. what kind of stress occurs at convergent plate boundaries / subduction zones / continental arcs?

1. compressive stress

1. what kind of stress occurs at transform plate boundaries? 

1. shear stress

1. possible behaviors of strain:

1. elastic

2. brittle

3. ductile

1. what is elastic strain? 

1. goes back to what it originally was, geologists don’t really care about this

1. what is brittle strain? 

1. permanent deformation, splitting things apart into broken surfaces

1. what is ductile strain? 

1. permanent deformation, rock bends or flows without breaking

1. difference between brittle and ductile strain: 

1. brittle cracks and fractures under stress, more likely to happen near surface and cooler places

2. ductile rocks bend or flow without breaking, happens deeper where it’s hotter and under more pressure

1. relationship between stress and strain:

1. stress happens before strain

2. everything has period of elastic deformation, certain amount of stress applies but material will return to original shape

3. surpass elastic limit, ductile deformation will occur until fracture (ductile limit)

1. factors that dictate and control brittle and ductile deformation: 

1. strain rate → how quickly force is applied

2. temperature 

3. confining pressure, how much surrounding force is applied 

4. fluid presence / absence

1. what role does strain rate play in brittle and ductile deformation? 

1. fast → brittle, rock breaks

2. slow → ductile, rock bends / flows

1. what role does temperature play in brittle and ductile deformation? 

1. low temp, molecules move slower → brittle (rock snaps)

2. high temp → ductile (rock softens and flows)

1. what role does composition play in brittle and ductile deformation? 

1. quartz / feldspar / olivine→ more brittle

2. clay / calcite→ more ductile

1. what role does confining pressure play in brittle and ductile deformation? 

1. shallower depths, low pressure → brittle

2. deeper, high pressure → ductile

1. what influence does water have on brittle and ductile deformation? 

1. dry → brittle

2. wet → ductile

3. water in system lubricates it and decreases friction, allows rock to act in more ductile fashion

1. difference between brittle vs. ductile behavior of igneous & metamorphic and sedimentary rocks: 

1. igneous & metamorphic → made of strong minerals, tend to be brittle unless deep / hot

2. sedimentary rocks → weaker minerals, tend to be ductile, especially when wet

1. at what depth do faults usually occur?

1. ~0-15 km 

2. mostly felsic, silicate, granitic composition

3. less pressure, rocks are more likely to break

1. why do rocks in the upper mantle behave differently? 

1. composed of peridotite and ultramafic composition

2. different period where they behave differently

1. what does ductile deformation result in? 

folding

1. what kind of folds are there? 

1. anticline and syncline

1. anticlines concave ____________

downward

1. synclines concave ____________

upward

1. where is the oldest material in anticlines? 

1. in the core of the fold

1. where is the youngest material in synclines? 

1. in the core of the fold

1. which direction do beds dip in anticlines? 

1. away from each other and the core of the fold

1. which direction do beds dip in synclines? 

1. towards each other and the core of the fold

1. what is the hinge of a fold? 

1. parallel to top of fold and fold axis

1. what is the axis of a fold?

1. imaginary line which generates the fold

1. if the hinge of a fold is horizontal, the fold is ____________

1. non-plunging

1. if the hinge of a fold is non-horizontal, the fold is __________

plunging

1. anticlines plunge in the direction the fold __________

closes

1. synclines plunge in the direction the fold __________

opens

1. what are monoclines? 

1. step-like folds, where the ground is mostly flat, but there’s a steeper section that connects the flat parts

1. what are domes? 

1. anticlines that plunge on all sides

1. where is the oldest and youngest formation on domes? 

1. youngest on the outside

2. oldest exposed in the center on the surface

1. what are basins? 

1. depression features where layers are tilted towards each other

1. what do faults represent? 

1. where rocks have broken in the past and may break again in the future

1. two primary types of faults: 

1. dip-slip

2. strike-slip

1. what kind of dip-slip faults are there? 

1. normal 

2. reverse / thrust

1. what is the motion in strike-slip faults? 

1. either parallel to dip or parallel to strike

1. what is the Basin and Range Province? 

1. region in the western US characterized by alternating mountain ranges and valleys 

2. valleys (basins) are separated by mountain ranges, creating basin and range topography

1. what is the hanging wall in a fault system? 

1. block above the fault

1. what is the footwall in a fault system? 

1. block below the fault

1. difference in movement between normal and reverse / thrust faults

1. normal fault has downward movement of hanging wall

2. reverse / thrust fault has upward movement of hanging wall

1. what are regions of horst and graben? 

1. terms used to describe landforms created by tensional forces

1. what is a horst region? 

1. upward block of the earth’s crust that is raised between two faults

1. what is a graben region? 

1. downward block of the earth’s crust that is lowered between two faults

1. what are fault scarps? 

1. surface features of some faults

2. steep slopes or cliffs formed when a fault causes vertical movement of the ground

1. what are strike slip faults?

1. have motion in horizontal direction 

1. where is the greatest amount of deformation typically found? 

orogenies

1. what are orogenies? 

1. mountain-building events caused by plate collisions

1. what are cratons? 

1. oldest, most stable parts of Earth’s crust

1. what are orogens? 

1. zones or belts where mountains form during an orogeny (mount-building event)

1. why do mountains still exist? 

1. they do not become too tall because of balance between uplifting and erosion of material from the peaks