Science Unit 2

Where does most of Earth’s precipitation occur?

Over Ocean

As water is precipitated onto the land, where does it go? Where does most of the water on land end up?

It goes to the ocean; most water ends up in glaciers and ice caps.

Distinguish between porosity and hydraulic conductivity.

Porosity is the volume of pore space in soil; hydraulic conductivity measures the ability of water to move through soil.

If a hole is dug in the unsaturated zone, does it fill with water? Why or why not?

It does not fill with water because pores are only partly full of water.

Compare and contrast the unsaturated zone with the saturated zone.

The unsaturated zone has pores partially full of water; the saturated zone has pores filled with water.

What types of soil allow the greatest amount of rainfall to soak in?

sandy soil with good hydraulic conductivity

What is an artesian system and how is it formed?

An artesian system is a confined aquifer. The aquifer is sandwiched between low-permeability layers with water pressure from water above forcing water to flow out of the ground.

Describe the consequences of over-pumping groundwater.

land subsidence; wells go dry

How does rainwater naturally become acidic? How does this affect limestone?

Carbon dioxide in the air creates carbonic acid in water that dissolves limestone.

How do stalactites and stalagmites form?


Stalactites form as water containing calcium carbonate drips from the roof of a cave and evaporates leaving behind limestone; stalagmites form on the floor of the cave by the same process.

Name three erosional features caused by groundwater in carbonate rocks.


caves, caverns, and sinkholes

What is the difference between a cave and a cavern?

Caverns are large caves.

What is stream gradient, and how does it affect stream velocity?

Gradient is the drop divided by the distance; the greater the gradient the faster the stream.

What happens to stream speed when the discharge of a stream increases?

The stream speed usually increases, but if the channel geometry changes the speed could actually slow down.

How does the shape of a stream channel affect flow?

Rounded, deep channels have less friction and higher speed than shallow, flat-bottomed channels.

Which transports more sediment: a laminar flow or a turbulent flow? Why?

Turbulent flow because it lifts particles into the flow and slides them along the channel.

Describe three ways that flowing water erodes a stream channel.

chemically, hydraulically, and by abrasion

What factors are responsible for the formation of a stream valley?

Water erodes material forming a channel, and gravity pulls material downhill on either side of the channel creating a V-shaped valley. The stream carries away sediments.

Under what conditions do curvy, meandering rivers form along a floodplain?

when a river slows changing from eroding downward to eroding side-to-side

What types of streams and stream valleys do we generally find in high, mountainous regions?

fast-moving streams with rapids and V-shaped valleys

Streams transport great quantities of sediment from one place to another. What is the size range of the particles that can be carried by a fast-moving stream?

from the smallest particles of clay to large pebbles and cobbles

What is a delta?

a fan-shaped deposit of sediment where a river meets a sea.

How is a glacier formed?

A glacier is formed when snowfall is compacted into ice that flows under its own weight.

In what two main ways do glaciers flow?

sliding downslope and internal plastic deformation

Under what conditions does a glacier front advance? Under what conditions does it retreat?

Advance: when accumulation exceeds ablation Retreat: when ablation exceeds accumulation

What is the most common depositional landform created by glaciers?

moraines

What erosional features are likely found in an area of alpine glaciation? (See Figure 22.37a).

U-shaped valleys, cirques, and horns

How do sand dunes migrate?

Wind blows sand grains from the windward to the leeward slope.

How are ripple marks formed?

by lift and deposition of sand grains by wind or flowing water

Rank, from greatest to least amounts, the distribution of Earth’s freshwater:

(1)Polar ice caps and glaciers, (2) groundwater, (3) streams, rivers, and lakes, (4) soil moisture.

What is a perched water table?

Water that has accumulated in a region above the water table in the unsaturated zone. This water is trapped by an impermeable rock or soil layer.

Which basin—Pacific or Atlantic—receives water from the Colorado River?

Pacific

Which receives water from the Rio Grande?

Atlantic

What are these deposited sediments called?

Beds

How are beds laid out?

Sediments are deposited layer up on layer, horizontally.

Put in order, from beginning to end, the steps in stream formation:

(1)Raindrops strike that ground, (2)runoff, (3)water begins to run downslope, (4)gullies form.

Give the sequence in the evolution of a stream from least to most to overlap them:

(b) rapids, (a) meandering pattern, (c) delta

Going from offshore toward the shoreline, rank these according to sediment size:

(d) clay, (c) sand, (b) pebbles, (a) cobbles

How does a glacier grow in size?

A glacier grows in the winter as snow builds on the surface. Glaciers grow in size by a process called accumulation, which is also the amount of snow added.

In the continental United States, what type of glacier is more common: alpine or continental?

Alpine

What land features are formed from glacial deposits?

outwash plains

Which of the three agents of transportation—wind, water, and ice—transports the largest boulders?

Ice

Which of the three agents of transportation—water, ice, and wind—transports only small rocks?

Wind

What type of stream is associated with the formation of an oxbow lake?

meandering stream

What is the dominant fluvial process in a clear, sediment-poor stream moving down a steep slope?

downcutting

Which processes result in the widening of the floodplain of a meandering stream?

undercutting and lateral erosion

Where do deposition and erosion of material occur along a meander?

Deposition occurs on the inside of the meander, whereas erosion occurs on the outside.

What is an oxbow lake?

A meander that has been cut off from the original stream channel

ow are oxbow lakes formed?

Oxbow lakes form when one meander erodes into another, cutting off water to part of the stream channel.

What is a meander scar?

a landscape feature formed after an oxbow lake dries up

What are cross beds?

inclined layers in sediment or sedimentary rocks that reveal the direction of wave or wind transport

What do cross beds represent?

the moving front of a ripple or dune

What is the relationship between water currents and cross beds?

Cross beds sit at an angle to current direction.

Why do dunes migrate?

Wind erodes material on the back side of the dune and deposits it on the front side of the dune.

How does the water table change around a pumping water well?

The water table elevation decreases.

What is the cone of depression?

the shape that the water table takes on near a pumping well

When will a cone of depression stop enlarging?

when the amount of water flowing toward the well equals the amount of water being pumped out of the well

When might a well, Well A, go dry?

when the cone of depression of a second well intersects the deepest part of Well A

How can pieces of rock in contact with a stream bed move?

rolling, sliding, bouncing

Complete this analogy: Bouncing is to sand as suspension is to_____________.

clay

Complete this analogy: Sliding is to gravel as dissolution is to_____________.

ions

Which of the following are part of the bed load?

Gravel and sand

What are the three types of loads carried by streams?

bed load, suspended load, dissolved load

What is suspended load?

the fine-grained particles that travel in the water column above the stream bed

Which of the following statements is true about erosion?

Erosion varies from place to place.

Where do valleys tend to form in a landscape?

Valleys form where rock layers are easily erodible (soft).

How much of Earth's surface water exists in the oceans?

Almost all of Earth's surface water exists in the oceans.

hich ocean is Earth’s largest?

the Pacific Ocean

Where is most of Earth’s freshwater found?

as ice at Earth's surface

What does the hydrologic cycle describe?

The hydrologic cycle describes how liquid and gaseous water move between the ocean, atmosphere, and land.

How does water get from the oceans onto land?

Ocean water evaporates to form gaseous water and moves into the atmosphere, where it condenses into liquid water and falls out of the atmosphere to land as rain.

What would happen to atmospheric water if Earth were mostly covered with land?

The atmosphere would contain less water.

What would happen to the oceans if surface runoff and groundwater flow did NOT occur?

The oceans would become smaller.

What is a floodplain?

a flat surface next to a river channel

What is a natural levee?

a ridge of flood deposits next to a river channel

How does the formation of a natural levee impact flooding?

Natural levees raise the height of the stream channel, reducing the amount of flooding that will occur on the floodplain.

How do pieces of rock move under the influence of wind?

rolling, sliding, bouncing, suspension

What property of a piece of material will most directly determine how it is carried by wind?

Size

What is dust?

the particles carried in suspension by wind

What is it called of the elevation of a water table above a particular location-usually sea level?

Hydraulic head

What is the Karst regions?

Characterized by soft rolling hills or sharp, rugged surface, and areas where sinkholes, caves, and caverns define the land surface.

Infiltration of water is controlled by:

Intensity and duration of precipitation, prior wetness condition of the soil, soil type, slope of the land, and nature of the vegetative cover.

What is a drainage Basins?

Land area that contributes water to a stream that is separated by drainage divides. With the largest divides are continental divides.

Relative dating does not tell the actual date of rock formation, it tells the _______.

time of rock formation in relation to other events in Earth's past

To match various rock outcrops over a large area, geologists use the principle of _______.

lateral continuity

With radiometric dating, scientists measure the _______.

ratio of a radioactive isotope (parent material) to its decay product (daughter material)

The geologic time scale is based on _______.

the relative ages of rock layers and their fossils

In a thick bed of sedimentary rocks we find an igneous dike. The order of formation is

sedimentary before igneous

In a sequence of rock layers we find trilobite fossils at the bottom of rock layer 1 and dinosaur fossils directly above the fossil trilobites in layer 2. There are inclusions of trilobites in layer 2. We conclude that

by inclusion and faunal succession, layer 1 is older than layer 2.

An assumption that Earth processes occurring today have always occurred is called

uniformitarianism.

The theory that different forms of animals throughout Earth's past occurred in a definite order is called the principle of

faunal succession

In any sequence of sedimentary rock layers that have not been subjected to stress, you would expect to find

older horizontal layers at the bottom with younger horizontal layers at the top.

The principle of faunal succession states that

fossil organisms follow one another in a definite, irreversible time sequence.

The principle of original horizontality states that each

new layer of sediment is laid down nearly horizontally over older sediment.

The rather simple idea that, unless disturbed, younger sedimentary layers overlie older layers, is referred to as the principle of

superposition

In a sedimentary rock that contains inclusions of metamorphic rock, the inclusions must be

older than the sedimentary rock

The five principles used to determine the relative ages of rock include original

horizontality, superposition, cross cutting, inclusion, and faunal succession.

Radiometric dating is based on

proportions of radioactive isotopes and their decay products

Radiometric dating assumes that, once a mineral has crystallized, any daughter product results only from the decay of the original unstable parent. Some complications are

"time clock resetting" due to metamorphism, and product leakage that yields false age estimation.

The process where an element spontaneously changes into a different element (transmutation) by a change in the nucleus of an atom is called

radioactive decay