Geography 101 Mod 3 Study Guide

Most rocks contain

Oxygen

Silicon

Aluminum

Iron

Calcium

Smaller amounts of other elements

Geological Forces

Shapes earths surface

Tectonic processes

Create landforms

Gradational processes

Reshape landforms

Mineral

A chemical combination with specific hardness, density, definite crystalline, and structure

Three most common minerals found in the earths surface

Quarts

Potassium

Feldspar

Silica

Magma

Underground molten material

Lava

Molten material that has emerged onto the earth's surface

Intrusive Igneous Rocks

Solidifies at depth, longer cooling times, and results in larger crystals. Formed from magma

Granite

Intrusive igneous rocks formed from magma, rich in silicates, lighter color, lower density

Gabbro

Intrusive igneous rocks formed from magma, rich in metallic, higher in density, darker color

Extrusive Igneous Rocks

Rock solidified from molten material (magma) that has flowed from beneath the earth's surface onto it. Shorter cooling times, and results in smaller crystals

Rhyolite

A fine-grained, felsic, igneous rock made up mostly of feldspar and quartz.

Extrusive version of granite.

Basalt

A dark, dense, igneous rock with a fine texture, found in oceanic crust.

Extrusive version of Gabbro.

Pumice

A very light and porous volcanic rock formed when a gas-rich froth of glassy lava solidifies rapidly.

Obsidian

A usually black or banded, hard volcanic glass that displays shiny, curved surfaces when fractured and is formed by rapid cooling of lava

Sedimentary Rocks

Rock formed by the accumulation of particles of gravel, sand, silt, and clay that were eroded from already existing rocks and laid down in layers.

Three types:

- Clastic

- Chemical

- Organic

Clastic Sedimentary Rocks

Sedimentary rock that forms when fragments of preexisting rocks are compacted or cemented together.

Conglomerates

- Mix of fine and course particle

- Clastic Sedimentary

Sandstone

- Formed by cementing grains of sand over time

- Clastic sedimentary

Silstone

- Generally composed of very small quartz grains

- Clastic sedimentary

Shales

- Made from layered clay

- Clastic sedimentary

Chemical Sedimentary Rocks

Precipitated from chemical solutions secreted by organisms

Limestone

- Consisting mainly of calcium that was deposited by the remains of marine animals

- Chemical sedimentary or organic sedimentary

Organic Sedimentary Rocks

Formed from remains of living organisms

Coal

- A fossil fuel that forms underground from partially decomposed plant material

- Organic sedimentary

Petroleum

- Oil and oil products in all forms, such as crude oil and unfinished oils

- Natural gas is a gaseous form, crude oil is a liquid form, and tar/asphalt is the solid form

- Organic sedimentary

Metamorphic Rocks

Rocks that have been changed (metamorphosed) when exposed to:

- High temperatures and pressures

- In the presence of water

Slate

- A type of rock that was once shale rock formed by heat and pressure

- Used for blackboards & roof shingles

- Metamorphic rock

Marble

- Rock that was once limestone

- Metamorphic rock

Gneiss

- Banded. Made up of granular mineral grains. It typically contains abundant quartz or feldspar minerals.

- Metamorphic rock

Earth's Age

~ 4.6 billion years

Alfred Wegener

First proposed that the Earth's landmasses are pieces of a giant supercontinent that existed hundreds of millions of years ago

Pangea

The super continent which contained all the plates together

Continental Drift

The hypothesis that an original single landmass (Pangaea) broke apart and that the continents have moved very slowly over the asthenosphere to their present locations.

Continental Drift vs. Plate Tectonics

Continental drift proposed that continents move, while plate tectonics explains how and why they move as parts of tectonic plates.

Earth's Plates

Earth's plates are large pieces of the Earth's crust and upper mantle that slowly move across the planet's surface.

Continental Plates

THICK and LIGHT lithospheric plates that are mostly made of silica

Oceanic Plates

THIN plates that form the ocean floor, HEAVIER than continental plates. Contains more metallic ions

Convection Currents

In the asthenosphere; causes the plates to move slowly across the Earth's surface (2-5 inches/year)

Divergent Plate Boundary

- Two tectonic plates move away from each other

- Allows magma to rise and form new crust.

- Can create mid-ocean ridges, rift valleys, volcanoes, and earthquakes

Convergent Plate Boundary

- Two tectonic plates move toward each other and collide

- One plate may be forced beneath another (subduction), or both may push upward

- Can create mountain ranges, volcanoes, deep-ocean trenches, and earthquakes

Transform Plate Boundry

- Two tectonic plates slide horizontally past each other

- Crust is neither created nor destroyed

- Creates faults and frequent earthquakes

Natural Hazards Associated with Plate Movement and Where They Most Likely to Occur

- Earthquakes, volcanic eruptions, landslides, and tsunamis. - Most likely to occur near plate boundaries, where tectonic plates collide, separate, or slide past each other.

Hot Spots

Areas of volcanic eruption due to a rising plume of molten material

Diastophism

The deformation and movement of Earth's crust caused by tectonic forces, including warping, folding, and faulting

Warping

The broad bending or uplifting/sinking of Earth's crust over a large area without breaking the rock

Folding

Occurs when rock layers are compressed and bend rather than break, often forming features such as mountains, anticlines, and synclines

Faulting

Occurs when stress causes rocks in Earth's crust to break and move along a fracture called a fault. Faulting is commonly associated with earthquakes

Tsunami

A series of large ocean waves caused by the sudden displacement of water, commonly from an underwater earthquake caused by movement along a fault

Composite Volcano (Stratovolcano)

- Steep, cone-shaped volcanoes made of alternating layers of thick lava and pyroclastic material

- Most commonly associated with plate convergence and subduction.

- Hazards include explosive eruptions, ash clouds, pyroclastic debris/flows, hot mudflows, and earthquakes

- Generally considered the more dangerous of the two types because their eruptions can be highly explosive

Shield Volcano

- Broad volcanoes with gentle slopes formed by thin, runny lava flows

- Most commonly associated with plate divergence or hot-spot activity

- Their eruptions are usually quieter and less explosive.

- Their main hazards include lava flows and forest fires.

Weathering

- The breakdown and decomposition of rocks and minerals in place (involves no movement)

- Occurs at or near the Earth's surface

- Can occur mechanically such as frost wedging and root action, or chemically, such ass oxidation or carbonation

Mass Wasting

- The movement of rock, soil, and other weathered material downslope due to gravity

- Includes landslides, mudflows, earthflows, and soil creep

- Factors that can contribute to mass wasting include steep slopes, heavy rainfall or water saturation, freeze-thaw cycles, weathering, earthquakes, and loss of vegetation

- Gravity is the only factor necessary for mass movement to occur

Erosion

- The removal and transportation of weathered material by running water, wind, and glaciers

- Primarily relies on these moving agents rather than gravity alone

Mechanical Weathering

The physical breakdown of rocks into smaller pieces without changing their chemical composition; common in dry and/or cold climates

Frost Action

- Water enters cracks and spaces in rocks then freezes

- Water expands when it freezes and pushes the rock apart

Salt Crystallization

- Groundwater moves through pores and cracks in rocks and then evaporates, leaving salt crystals behind

- As crystals grow, they exert pressure that forces the rock particles apart

Root Action

- Plant roots grow into cracks in rocks

- As roots grow larger, they exert pressure on the rock, causing it to break apart and disitnegrate

Chemical Weathering

-Occurs when chemical agents, often combined with water, decompose rocks and minerals and change their chemic structure

- Common in warm, humid climates

Oxidation

- Occurs when oxygen combines with minerals in rocks, especially iron and aluminum, to form oxides

- Chemically alters and weakens the rock

Hydrosis

- Occurs when minerals react with water and are chemically charged into new minerals

- Aluminosilicate minerals such as potassium feldspar can react with water to form clay

Carbonation

- Occurs when water combines with carbon dioxide to form weak carbonic acid

- This acid reacts with and dissolves limestone; can eventually create caverns and other karst features

Landslide

- The rapid movement of large amounts of rock, soil, and debris downslope

- Can occur very quickly, often within seconds or minutes

- Can destroy buildings, roads, and other structures and can cause injuries and death

Mudflow

- Occurs when weathered soil and sediment become saturated with water, often after heavy rainfall, and rapidly flow downhill as a slurry

- Occurs quickly, within minutes or hours, and can bury or damage buildings, roads, and vegetation

Earthflow

- Occurs when weathered soil and sediment become saturated with water and flow downslope under their own weight

- Generally slower than mudflows and may occur over hours, days, or longer.

- Can damage roads, buildings, and other structures in their path

Soil Creep

- Very slow movement of soil downhill, often caused by repeated freeze-thaw cycles

- Occurs gradually over years or longer and usually isn't an immediate danger

- Over time it can damage foundations, roads, fences, and other structures

Three Factors That Affect the Ability of Running Water to Erode Landforms

- Amount of Precipitation: The more precipitation an area receives, the more water flows across the surface, increasing the water's erosional force. Raindrops can also dislodge soil particles

- Slope: Water flows faster on steeper slopes, giving it more erosional power. Longer slopes also give water more distance and time to gain speed, increasing erosion

- Rock and Vegetation Cover: Rocks and vegetation protect the soil from moving water and rainfall. Areas with more rock and vegetation cover experience less erosion, while areas with little or no cover experience more erosion

Stream Load

- All of the material being transported by a stream

- Includes dissolved load, suspended load, and bed load

Dissolved Load

Consists of materials dissolved in the stream water and carried in solution, such as carbonate and sodium salts

Suspended Load

Consists of fine materials, such as silt and clay, that are carried within the water by the stream's current

Bed Load

Consists of larger materials, such as sand, gravel, and boulders, that move along the bottom of the stream

Stream Delta

- Landform created by the deposition of sediment where a river or stream enters a relatively still body of water, such as an ocean, lake, or bay

- As the stream enters the still water, it slows down and can no longer carry as much sediment, causing sand, silt, and other materials to be deposited.

- Over time, these deposits build up and form a delta

Falls

- Occur along steep stream channels where water experiences a sudden drop in elevation

- The rapidly moving water causes strong erosion, helping shape and alter the falls over time

V-Shaped Valleys

- Deep, narrow valleys created by strong downward stream erosion in steep regions

- As the stream cuts downward into the landscape, erosion and mass movement along the sides produce the characteristic V shape.

Floodplains

- Wide, relatively flat areas alongside rivers

- They form when rivers overflow during floods and deposit sediment across the surrounding land

Oxbow Lakes

- Abandoned meander loops

- They form when a meandering river changes course and cuts off on of its loops, leaving the old channel separated from the main river

Natural Levees

- Raised areas along riverbanks formed by sediment deposited during the floods

- When floodwater leaves the river channel, its slows down and deposit heavier sand and silt near the riverbank, gradually building the levees higher than the surrounding floodplain

Alluvium

Loose sediment, such as sand, silt, clay, and gravel, that has been transported and deposited by flowing water

Alluvial Fan

- Fan-shaped deposit of silt, sand, and gravel that forms when a mountain stream reaches flatter terrain and rapidly slows down, causing it to deposit its sediment

- Larger gravel is deposited first, followed by sand, silt, then clay

- Similar to the stream delta, both form when flowing water slows and deposits sediment, producing a generally fan/triangular -shaped landform

Arroyo

A deep, steep-sided stream channel carved by rapidly moving water in an arid region.

Wash

- Usually a dry stream channel in an arid region that carries water after rainfall

- Braided channels left behind by water rushing across alluvial plains

Buttes and Mesas

- Elevated, flat-topped remnants of upland or plateau regions left behind by erosion

- Generally larger and broader than a butte

Aquifer

A saturated underground zone that stores and transmits groundwater

Water Table

The upper limit of an aquifer

Solution

The process in which groundwater dissolves soluble rock materials

Cavern (cave)

- A large underground chamber, commonly formed in limestone as groundwater dissolves the rock

- Can result from rising and falling water tables in limestone regions

Stalactites and Stalagmies

- Both are limestone/mineral deposits that form inside caves

- Stalactites form on and hang from cave ceilings, while stalagmites from upward from cave floors

Sinkhole

A surface depression that forms when an underground cavern collapses, causing the land above it to sink

Karst Topography

- The landscape that develops across large limestone regions due to the dissolving action of groundwater.

- Characterized by features such as sinkholes, caverns, underground streams, and other solution features

Glacier

A large mass of ice that forms where snowfall exceeds snowmelt and evaporation

Permafrost

Ground that remains frozen for at least two consecutive years

Glacial Trough

Deep, U-shaped valley created by the movement and erosion of a glacier

Fiord/Fjord

A glacial trough along a coastline that becomes filled with seawater as sea level rises

Cirque

A bowl-shaped valley or depression carved by a glacier in a mountainous area

Arête

A sharp, knife-like ridge formed between two adjacent glaciers or glacial valleys

Till

Unsorted rock and sediment deposited directly by a glacier as it moves or melts

Outwash Plain

An area of alluvial material deposited by streams of meltwater flowing away from a glacier

Longshore Current

A current that moves parallel to the shoreline and transports sand and sediment along the cost

Spit

A narrow deposit of sand that extends outward from the coastline into the water