Download Weathering: breakdown of rocks into sediments The difference

Weathering: breakdown of rocks into sediments
The difference between mechanical & chemical weathering is: mech breaks rocks; chem changes the
composition of the rock (e.g. iron into iron oxide)
Sort terms as being mechanical/physical or chemical weathering:
Mechanical: root splitting bedrock, exfoliation, ice wedging, frost action [last two are the same!]
Chemical: acid rain, dissolving minerals, oxidation
Explain what is happening in each of these three images:
Roots splitting rocks (mech)
Frost action/Ice wedging
Soil creep
Rates of Weathering
• Climate
o Warm & humid: more chemical weathering
o Cold and/or dry: more mechanical weathering
o Frost action needs: wet climate alternating between below freezing & above freezing
• Surface area: increased surface area (smaller pieces) increased rate of weathering
• Mineral composition
o More resistant to weathering/erosion size/shape after weathering will be rough & large
o Less resistant size/shape after weathering will be smooth/round & small
• If all these rocks have been exposed to the same weathering
agents over the same period of time, and started at the same
height, explain why X is so much deeper than Y now.
X is probably a softer rock, less resistant to weathering in this
environment
Erosion: movement of sediments by wind, water, gravity or glaciers
• Running Water *most important agent of erosion/deposition on Earth
o Examples: delta, meander
o Sediment Characteristics: round, smooth
o Valley shape: V-shape
• Gravity
o Fast-moving examples: talus, landslide/mudflow
o Slow-moving examples: creep, slump
o Sediment Characteristics: angular, sharp (rough)
• Wind
o Examples: sandblasting, deflation
o Sediment Characteristics: semi-rounded, pitted
• Glaciers
o Landforms: grooves, till, erratic, striations, drumlins, finger lakes, kettle lakes
o Sediment Characteristics: semi-rounded, scratched
o Valley shape: U-shape
Stream
• Increased slope increased velocity
• Increased velocity increased erosion
• Meander: bend or curve in a river
o Label this stream with an E
where erosion is taking place,
and a D where deposition occurs
o Label the left diagram.
Deposition/Sedimentation: process by which sediments are released, settled from, or dropped from an
erosional system
• Velocity
o Increased velocity less deposition, more erosion
o Decreased velocity more deposition, less erosion
• Sediment Size
o Increase size faster settling rate
o Decrease size slower settling rate
• Sediment Density
o Increase density faster settling rate
o Decrease density slower settling rate
• Sediment Shape
o Round faster settling rate
o Flat slower settling rate
• Sorted Sample: sediments separated by size or shape:
o Happens in water or wind
•
Unsorted Sample: sediments of different size or shape mixed
together:
o Happens in glaciers or gravity
•
Which of following shows the result when you drop one sample of mixed sediments into standing
water?
* b/c it shows one instance of deposition, with biggest (fastest) particles on the
bottom, getting progressively smaller near the top of the sample
•
Which of the following correctly shows the deposition of sediments where a river runs into a lake or
ocean?
*
*
*b/c shows progression of largest (gravel) deposited first, then next largest, then smallest furthest
away
•
If the four particles below were dropped at the same moment, list the
order in which they will settle on the bottom of their beakers.
A settles first (shortest time), B settles second, C third, and D
settles last (longest time)
•
Draw an arrow to show the direction the agent of
erosion/deposition was moving to create the landform in this
picture. What deposited the sand?
longshore drift @ jetties
Soil
Formed from weathering without erosion
To increase amount of soil:
o increase biological activity (thicker humus layer)
o increase weathering (more sediments)
o decrease erosion (so sediments aren’t washed away)
• Soil Profile (side view of soil layers or horizons)
o In which horizon would you find the following:
Horizon A – humus, most weathering, organic
material
Horizon B – clay
Horizon C – slightly weathered rock fragments
Put the following pictures in the correct order for soil development.
•
•
II, IV, III, I •
•
Residual Soil: soil matching & formed from local bedrock
Transported Soil: soil that does not match local bedrock – most common in NY b/c of glaciers
Groundwater
Which diagram below best represents the most common arrangement of zones in a water table?
Permeable layers of rock and sediment that store and carry enough groundwater to supply wells are called
aquifers.
Porosity: percent of a material that is empty
pore space
• Effect of particle size: NO EFFECT
•
•
Permeability: how quickly water travels through
a material
• Effect of particle size: larger is more
permeable
Effect of particle sorting: sorted is more
porous
•
Effect of particle sorting: sorted is more
permeable
Effect of particle shape: round is more
porous
•
Effect of particle shape: rounded is more
permeable
Draw the appearance of the water table after pumping from this well:
the cone of depression
List formations found in an area of karst topography:
Sinkholes, caves, fissures (cracks) in the ground
Rock Cycle
Fill in the rock cycle below with the processes that form each rock.
Classify the following rock names: basalt, breccia, coal, conglomerate, gneiss, granite, limestone, marble,
obsidian, pumice, quartzite, rock salt, sandstone, schist, shale, siltstone, slate
Igneous
Metamorphic
Sedimentary
Basalt
Gneiss
Breccia
Granite
Marble
Coal
Obsidian
Quartzite
Conglomerate
Pumice
Schist
Limestone
Slate
Rock salt
Sandstone
Shale
Siltstone
Be able to identify a rock sample as igneous, sedimentary, or metamorphic. For example, state whether each
rock diagram below is igneous, metamorphic or sedimentary. Then state why you made that determination &
the environment that created it.
Rock Type: metamorphic
Why: foliated
Environment: convergent
boundary
Rock Type: sedimentary Rock Type: igneous
Rock Type: sedimentary
Why: pebbles
Why: holes/bubbles
Why: fossil
Environment: riverbed
Environment: volcano Environment: river/beach
Why doesn’t obsidian have crystals? Cooled too quickly at earth’s surface near volcano
Large crystals in igneous rocks are caused by long cooling, deep underground in magma