Mini Lab Exam 1

how science works

[new tech, practical probs, curiosity, personal motivation, serendipity, surprising observation] into exploration and discovery [making observations, asking questions, sharing data + ideas, finding inspiration, exploring the lit] back and forth to gathering data [hypothesis, expected results/observations, actual results/observations] + interpreting data [supportive/contradictory/surprising/inconclusive data may support a hypothesis, oppose a hypothesis, inspire revised/new hypothesis, or inspire revised assumptions] back + forth to community analysis + feedback [feedback + peer review, replication, discussion w/ colleagues, publication, coming up w/ new questions/ideas, theory building] + back + forth to benefits + outcomes [develop tech, address societal issues, build knowledge, inform policy, satisfy curiosity, solve everyday probs]

plate tectonics (2)

seafloor has record of magnetic reversals (paleomagnetism), Walter Alvarez wanted to look for new record moved onto land by plate tectonic processes

K-T boundary (5)

Cretaceous-Tertiary, dinosaur extinction 66 Ma + other things living on land (Walter thought it also applied to oceans), healthy fossil record w/ hi diversity on bottom, 1 cm layer of clay in middle, small fossils + lo diversity on top (unhealthy marine environment)

going hypothesis for K-T boundary (2)

major period of climate change (gradual), Walter wanted to estimate time represented in clay w/ things that steadily rain down to Earth’s surface

10Be (3)

decays to 10B (stable), more 10B = more time, ½ life of 1.36 MY (very small amount of 10Be)

Ir (6)

77 - heavy, rare on Earth but rains down, stable, more concentrated iridium (~0.1 parts per billion) would’ve implied slower deposition while less iridium (undetectably small amount) would’ve implied rapid deposition + sudden K-T transition, expecting 0.1 ppb but spiked to 3 ppb at clay boundary, confirmed by Alvarez in Italy + colleague in Denmark

major source of heavy elements (3)

supernovas (fits w/ prior hypothesis), would’ve also produced 244Pu (radioactive) which was found, chemists retested + found no plutonium (og set of samples were contaminated)

large object could’ve come in + hit Earth’s surface (5)

w/ additional testing object 10 km in diameter would be enough to cause large portion of biosphere (land + ocean) to go extinct, fine particles ejected into atmosphere block out sun + cause cooling + lack of photosynthesis for phytoplankton (base of marine food web) + land plants, much more rapid event than originally thought, published 1980 paper sparking wave of new research in clay layer + tsunami evidence, expect to find extinctions / impact debris / glass / shockwaves / tsunami debris / crater

topography (3)

the surface of the Earth, the shape of Earth’s surface as defined by elevation relative to sea level, variations can provide clues to geologic processes that are taking place both at + below Earth’s surface

topographic maps (9)

illustrate the 3D shape of Earth’s surface using 2D, important in public policy + planning (identify areas at risk of flooding, landslides, + other natural hazards), used as basis for geologic maps, tell topography w/ contour lines, lower left-hand corner tells age of map, depict the Earth as viewed from above, map scale info in bottom middle, key to maps of the surrounding area w/ the center square representing this map in bottom mid-right, map name + yr of publication in bottom left

geologic maps (8)

show the distribution of diff rock types + geologic structures (primarily faults + folds) across Earth’s surface, areas are shaded different colors to indicate different rock types (for example, sandstone and solidified lava flow / basalt), use lines/symbols/colors to communicate info abt the nature + distribution of rock units w/in an area, includes info abt geological contacts + their strikes + dips, made using careful field observations at numerous outcrops (exposed rocks at Earth’s surface) throughout the mapping area recording info such as rock type + the strike + dip of the rock layers, can also include relative age data if evidence found of relationships between the rocks using the principles of relative dating, 3D features (folds, etc.) displayed on 2D surface, viewed from above (floor plan to house)

topographic profile (6)

side-view of the elevations + slopes in an area, to visualize relief, an x-y graph w/ horizontal distance on the x-axis + elevation on the y-axis, excellent tools for visualizing 3D forms, drawn across line on topographic map, directional arrow points N

contour lines (11)

continuous lines of equal elevation, will always close to make a circle (inside of circle contains higher land / top of hill + outside lower land) or go off the map, every point on a contour line has the same elevation, close together in steep terrain + far apart in flat areas, create V patterns when they cross a stream valley w/ the tip of the V pointing uphill, contour lines on opposite sides of a valley or ridge always occur in pairs, do not touch or cross each other (except at a vertical wall or cave / cliff when they appear to merge, or an overhanging cliff where they cross + the contours representing the ground surface beneath the overhang are dashed), closed depressions have hachure marks on the downhill side (pointing inward), can be visualized as the shoreline of an ocean if sea level rose to that elevation, it’s possible to have >1 contour line representing the same elevation on a single topographic map, never branch / split / stop abruptly

index contour lines (2)

bold labeled contour lines, occur at a set interval of elevation

contour interval (2)

the difference in elevation between any 2 adjacent contour lines (not just index contour lines) on a topographic map, specified in the legend

relief

the difference in elevation between any 2 points

maximum/total relief

the difference in elevation between the highest + lowest points in a given area (such as the area shown on a map)

local relief

the difference in elevation between 2 nearby points (such as between a hilltop + a nearby valley)

scale (2)

expresses the relationship between distances on a map + corresponding distances in the real world, ratio scales have no units + apply to all units of measurement (for example, a scale of 1:10,000 indicates that 1 in on the map corresponds to 10,000 IRL + 1 mm on the map corresponds to 10,000 mm IRL)

what does 7.5 minutes refer to?

the map covers 7.5/60 = 0.125 degrees of latitude + 0.125 degrees of longitude

latitude + longitude (7)

latitude is horizontal lines like the rungs of a ladder, longitude is vertical lines, represented in units of degrees / minutes (‘) / seconds (‘‘), there are 60 minutes in 1 degree + 60 seconds in 1 minute, unless established elsewhere on the map latitudes are accompanied by N or S to indicate their position relative to the Equator + longitudes are accompanied by E or W to indicate their position relative to the Prime Meridian, shown along the edges of maps (but a 2nd set of coordinate labels which reference the U.S. National Grid System are shown too), look at the corners of the map to find the latitude + longitude of the map’s top + side edges

shape of Earth’s surface

the combined result of tectonic processes (compression, uplift, rifting, etc.) / weathering / erosion

erosion (2)

removal of sediment, dominates most areas of the continents as opposed to deposition

deposition

addition of sediment

soil (3)

loosely-deposited sediment, alluvium, relatively thin layer

bedrock (3)

under soil, layers, reflects that region’s deep geologic history, portions of bedrock layers that lie close beneath soil/alluvium layer have been shaped by millions of yrs of weathering + erosional processes, geologists need to identify + document the types + ages of rock that lie underfoot around the world + determine the spatial orientations of the rock layers in order to study Earth history, an important geological skill is visualizing how layers of bedrock intersect w/ the Earth’s surface (this intersection between geology + topography is the basis for geologic maps)

block models (6)

3D, block diagrams are images based on block models, blocks of wood or paper w/ geological structures marked on them, assist in visualizing how 3D geological structures in the real world can be represented in 2D on a map or in a geological cross-section, see cross-section view if you look at a block from along the side (also the view you see when driving thru the mountains + the roads have been cut thru the rocks, exposing structures in the rock you wouldn’t see otherwise) or map/plan view if you look from above, can see how rock layers are tilted in cross-section view

principle of original horizontality (2)

sedimentary rocks deposit in horizontal layers under the influence of gravity, in reality rock layers are more complicated + often tilted at an angle meaning changes have occurred since deposition (for ex, the rocks have been uplifted by tectonic activity + tilted), in some cases beds can be completely overturned (for ex in recumbent folds)

law of superposition

oldest rocks / sedimentary layers on bottom (because they had to be there 1st for the others to deposit on top of them)

geological contact

the planar surface between 2 adjacent rock units, each boundary between adjacent rock layers

fault

causes land to slip down but higher land may be eroded away leading surface to be flat but w/ sharp distinction between types/layers of rock

fold/bending (5)

happens deep below Earth’s surface (hi temp, hi pressure), uplifted + exposed then top eroded to be flat, syncline is a down-fold, arrowhead shape is due to the fact that a fold’s axis is angled down into the ground (plunging), characterized by same strike but dips pointing toward each other (in opposite directions), San Rafael Swell (structure seems pretty continuous, would’ve once been filled in w/ more relief but material in center was eroded away)

dip direction (8)

points down slope of rock layers, dip directions pointing opposite ways indicates fold, N/S/E/W, always perpendicular to strike, points in direction roof slopes down, direction of max downward slope of the angled plane, direction of drop of water would roll if following contact, shorter line / tick mark on symbol

strike (7)

the line formed by the intersection of a horizontal plane + an inclined surface/plane, follow stripes of layers, two directions (N + S), the direction the line points in (either direction) is the strike angle, points along roof ridge on top, water line when a lake intersects with/ the rock along the shoreline, longer line/bar on symbol

dip angle (7)

the angle between the horizontal plane (such as the top of a block in a block diagram) + the inclined surface (such as a geological contact between tilted layers) measured perpendicular to the strike line down to the inclined surface, indicates how tilted a rock layer is relative to horizontal (0 degrees) w/ larger angles indicating dips closer to vertical (90 degrees), higher angle = steeper, angle roof tilts, measured from the horizontal surface to the uppermost dipping bed, measured where the incline of a layer is at is maximum (also happens to be perpendicular to strike line), written next to tick mark showing dip direction on symbol

beds oriented in the same direction

have the same strike + dip

rule of Vs (3)

for contour lines but also useful for interpreting the direction that beds + other geological structures (for ex, faults) are tilted on maps, law of Vs for geological structures is more complicated than the rule of Vs for contour lines since there’s an additional layer of complexity when we add in the geology, you can usually determine dip direction of inclined beds by looking at the direction of the V that forms when the bed crosses a valley on a map

vertical beds (3)

no V shape is created in map view, bed cuts directly across valley w/out being deflected in either direction, feature is linear across the landscape despite the changes in the topography / contour lines (we would see the same pattern in the landscape for vertical faults or other vertical geological features)

inclined beds that dip in the opposite direction as the slope of the valley

V will point in the direction of the dip

inclined beds that dip in the same direction that the valley slopes (3)

situation is more complex, if the dip of the beds is steeper than the slope of the valley the V will point in the direction of dip, if the valley slopes steeper than the dip of the beds the V will point in the opposite direction of dip

horizontal beds (3)

the edge of the bed will intersect topography parallel to topographic contours, if the landscape is flat near the valley the bed will intersect in a straight line along the edge of the valley, if the landscape is sloping near the valley the bed will generate a V shape parallel to the contour lines in the valley

subduction zones (5)

transition from continental to oceanic crust happens at the lowest point in the trench where oceanic crust is subducting underneath the adjacent continent, earthquakes go from shallower to deeper as you move more towards the continental crust, volcanoes go in line parallel to coast along line of deepest earthquakes, convergent, downward pull of descending plates is the major driving force behind plate tectonics

volcanoes at subduction zones (4)

light stuff (volatiles, water) excised out of waterlogged subducting crust at ~100 km depth rises + interacts w/ (partially melts bc volatiles/water lower melting temp) asthenosphere, more buoyant / less dense melt/magma rises thru lithosphere + produces volcanic system in overriding plate, angle between surface + subducting plate can be found with tan(theta) = O/A = 100 km / distance between where plate is subducting + volcano, steep slab = volcano close to trench while shallow slab = volcano far from trench

bathymetry

ocean depth

transition from continental to oceanic crust (2)

the base of the continental slope + rise, where the abyssal plain begins + the transition to oceanic crust occurs

mid-ocean ridge (5)

plate boundary is the lowest point of the rift valley, shallow earthquakes are most common, ocean floor is youngest near middle + age increases as you approach the 2 ends, divergent (rift or spreading center), seafloor is elevated around midpoint bc crust is thinner at midpoint meaning asthenosphere is closer + seafloor there is hotter so it will expand (less dense) + rise

absolute plate motion

how fast the plates move relative to the interior of the Earth below the plates

relative plate motion

how fast the plates move relative to each other

transform faults (5)

San Andreas Fault, land looks wrinkled, divot line in middle w/ higher areas on either side showing a buildup of material, shallow earthquakes, leaky transform boundaries mean new oceanic crust is forming due to divergence but transform motion is still heavily involved (Gulf of California)

continent-continent convergence (6)

India + Asia, once-subducting plate has a lower elevation w/ volcanoes occurring on non-subducting side, oceanic crust broke off + plates began converging to form mountain range, plate boundary continually moves toward once-subducting plate w/ mountains being on non-subducting side, mostly very shallow earthquakes (0-33 km) w/ a few in the 33-70 km range + rare examples in the 70-150 km range, still colliding bc of subduction zone somewhere else that pulls plate along

geologic cross-section (9)

shows geologic features from the side view (ex: side views of block diagrams), similar to topographic profiles but also show rock types + geological structures present beneath Earth’s surface, legend (key to patterns used to ID each unit on cross-section, units ordered from oldest formation at bottom to youngest unit at top of legend), orientation of cross-section is the direction that the cross-section line makes on Earth (strike direction of cross-section line on geological map, indicate by writing corresponding direction at each end of cross-section like W + E), descriptive title (include letters used to ID line on og geological map), ratio and/or bar scale (vertical + horizontal scales should be the same, so you only need to include 1 scale), x-axis is distance along line on map + z-axis is elevation of the rocks (usually measured relative to sea level or another benchmark), structures may be drawn in w/ a dotted line above Earth’s surface to indicate rocks that were formerly present but that have since been eroded, dashed lines can also indicate position of the bottom of beds when you don’t have any evidence for their thickness or if you have some basis to know that they’ll end w/in the cross-section (for ex, sedimentary beds overlying metamorphic basement rock exposed elsewhere in the region)

Brunton compass (5)

can make measurements of strike / dip direction / dip angle, hold so that pointer points away from you + mirror points toward you, read dip angle on side where it meets little divot, read dip direction from top (long thing points toward dip direction), bubble level shows whether compass is level

compass bearing (2)

a strike or dip direction can be thought of as a compass bearing, the direction in which your compass needle points when you are using it to navigate

azimuth (9)

breaks compass down into 360 degree circle to specify strike directions more precisely than just compass quadrants for geologic mapping, think abt each # of degrees as the angle that each direction makes w/ 0 degrees (N), any strike or dip direction can be recorded very precisely as a bearing in degrees, N is 0 degrees or 360 degrees, E is 90 degrees, S is 180 degrees, W is 270 degrees, it’s unnecessary to record an azimuth for the dip direction bc it’s perpendicular to the strike direction, write as 030/55E (strike/dip angle + direction, could use SE)

right-hand rule for compass (4)

fingers point down dip, thumb points toward strike, dip direction is 90 degrees CW (to right) from the strike azimuth, strike is 0 degrees if dip direction is 90 degrees

sandbox models

among the most accurate at replicating the structure + deformation of fold + thrust belts, used by structural geologists to investigate the geometries + kinematics (movements) of faults + folds bc the deformational evolution of foreland fold + thrust belts / mountain ranges is difficult to study directly (since few of these tectonic systems are active today + those that are exhibit slow rates of deformation), sandbox can be tilted to mimic diff angles of basal faults