Science exam two

Why is coastal erosion a threat?

Natural process of moving rock from one location to another on hills. it destroys homes, roads, and habitats, while deposition can block navigation channels or alter ecosystems.

Why is deposition a threat?

The result of surface currents and waves bringing heat from the equator to the poles is. It reshapes coastlines, threatening communities, economies, and ecosystems.

Why are coastal processes of concern to many people?

Over half of the world’s population lives near coastlines.

What causes erosion and deposition along coastlines?

Wave energy, tides, currents, and storms erode or deposit sediments. Human activities (like damming rivers or building seawalls) can also disrupt natural sediment flow, worsening erosion in some areas.

The crest

Highest point of the wave

Trough

The lowest point of the wave

Wavelength

The distance between two crests or troughs- decreases as it breaks

What is the Coriolis Effect?

It’s the deflection of the moving objects (air or water) due to Earth’s rotation. Rightward goes to the northern hemisphere. Leftward in the southern hemisphere. Hurricane rotation

Why do waves form?

Waves form from wind.

wave height

the vertical distance from crest to trough- increases as it moves to shallow water

wave base

Depth at which wave motion stops (half the wave length)

Swash 

water moving up the beach after the wave breaks

Backwash

Water flowing back down the beach toward the ocean.

How does beach profile influence wave energy and plate tectonics?

Steep beaches (west coast beachs) create high energy. Gentle beaches (east coast) absorb energy better and experience more deposition.

Why are waves different on the West vs. East Coast of the U.S.?

The West Coast faces the open Pacific, where strong, long-fetch winds generate large, high-energy waves. The East Coast faces the Atlantic, which is narrower and more protected, leading to smaller, lower-energy waves.

What is a storm surge?

A rise in sea levels across the coastline caused by the combination of a hurricane's surface winds and where the coastline is located. causes rapid erosion

What is longshore drift and its effect?

It’s the movement of sediment along the coast by waves hitting the shore at an angle. It gradually shifts beaches down the coast, forming features like spits and barrier islands.

Sources of coastal sediment:

Rivers, cliff erosion, windblown sand, glaciers, and shells or coral from marine organisms.

Relationship between wave energy and sediment size:

High-energy waves move and deposit coarse materials (sand, gravel), while calm, low-energy conditions allow fine sediments (silt, mud) to settle.

Where to find fine vs. coarse sediment:

Fine sediment accumulates in sheltered areas like lagoons or the back side of barrier islands; coarse sand is found on open beaches with strong waves.

How do hurricanes and tsunamis affect coastal communities?

They cause flooding, erosion, infrastructure collapse, and long-term economic and ecological damage.

What is a hurricane and its relation to tropical cyclones?

A hurricane is a type of tropical cyclone—a rotating storm system forming over warm ocean water.

Hurricanes, typhoons, cyclones—differences:

• Hurricanes – Atlantic & NE Pacific

• Typhoons – NW Pacific

• Cyclones – Indian Ocean & South Pacific

Tropical depressions and storms:

A tropical depression has winds ≤ 38 mph.
A tropical storm has winds 39–73 mph.
A hurricane begins at ≥ 74 mph.

How hurricanes form:

They develop over warm ocean water (≥ 26.5°C / 80°F) with moist air and low wind shear. Rising warm air fuels rotation and intensification.

What controls hurricane spin and paths?

The Coriolis effect determines spin direction (counterclockwise in Northern Hemisphere, clockwise in the Southern). Global wind patterns and ocean currents steer their paths.

What is the eye of the hurricane?

A calm, clear center surrounded by the eyewall—the most intense part of the storm.

What happens as hurricanes make landfall?

They lose energy as they move over land (no warm water source) but can still cause flooding, wind damage, and tornadoes.

Hurricane Damage to people and property:

High winds, flooding, storm surge, infrastructure destruction, and long-term displacement of populations.

Shore profile and storm surge damage:

Flat, gently sloping coasts allow storm surge to reach farther inland, while steep coasts limit flooding but may suffer from wave impact erosion.

What is a tsunami and what causes them?

A tsunami is a series of large waves caused by underwater earthquakes, landslides, volcanic eruptions, or meteorite impacts.

What controls coastal erosion severity?

Wave energy, coastal geology, human activity, sea-level rise, and storm frequency.

Ways to deal with coastal erosion:

Beach nourishment, dune restoration, limiting development, and vegetation planting.

Ways to stabilize a shoreline:

Seawalls, groins, breakwaters, and revetments—but these can cause problems elsewhere by disrupting sediment flow.

How fast do tsunamis travel?

Up to 500–600 mph in deep water—about the speed of a jet airplane.

Canary Islands “mega-tsunami” likelihood:

Unlikely in the near future. Studies show the island slope is relatively stable, and catastrophic collapse scenarios are exaggerated.

How do we determine tsunami evacuation time?

By measuring the earthquake’s location, depth, and travel time of waves across the ocean using tsunami monitoring buoys and modeling systems.

How dangerous is flooding globally and in the U.S.?

Floods are the most common natural disaster in the U.S., causing about 100 deaths per year and billions in property damage annually.

Drainage basin

The land area that drains into a specific river or stream. Larger basins collect more water and sediment.

Drainage divide

The highland separating two drainage basins. Determines where rainfall flows.

Base level

The lowest point a river can erode to (usually sea level).Rivers can’t erode below this; if base level drops, erosion increases.

River channel

The physical path the river follows. Width/depth change with discharge and sediment load.

Floodplain

Flat area beside a river, built by periodic flooding. Important for storing excess water during floods.

Profile

The side view (cross-section) of a river from headwaters to mouth. Steep upstream, gentle downstream.

Gradient

Slope of the river channel. Higher gradient → faster velocity → more erosion.

Discharge

Volume of water flowing per unit time (Q = width × depth × velocity). Increases downstream.

Velocity

Speed of river flow. Higher gradient and discharge increase velocity.

Sediment

Material carried by the river. Faster water carries more and larger sediment.

Meandering Rivers

• Meandering: Curving, winding bends in a river.

• Where: Found in the lower (downstream) parts of rivers where gradient is gentle and sediment is fine.

• Erosion occurs on the outside of bends (cut bank); deposition occurs on the inside (point bar).

Gradient (Stream)

Steep, Gentle

Upstream: Steep, Downstream:Gentle

Velocity (Stream

Upstream: High, Downstream: Lower

Channel (Stream)

Upstream: Narrow, rocky, Downstream: Wide,Muddy

Erosion vs. Deposition (Stream)

Upstream: Erosion Dominates, Downstream: Deposition dominates

Floodplain (Stream)

Upstream: Narrow or absent, Downstream: Broad floodplain

Where are Flash Floods common

mountainous or arid regions (e.g., Colorado, Arizona).

Why do flash floods occur

Steep slopes, thin soils, and impermeable rock cause rapid runoff.

2013 Colorado Flooding

2013 Colorado Flooding: Resulted from extreme rainfall (over 15 inches in some places) and saturated soils. Water rushed down steep canyons, destroying towns and roads.

Where do Floodplain Floods occur?

Wide, low-lying valleys (like the Mississippi River).

How do Floodplain flood happen

Caused by long-lasting heavy rain or snowmelt over large areas.

Flash flood

Sudden, localized, short-term; more deaths.

Floodplain floods

Slower onset, widespread; more property damage.

Recurrence interval

Average time (in years) between floods of a given size.

Discharge relationship

Larger discharges (bigger floods) have longer recurrence intervals.

Flood Hazard Map

• A map showing areas likely to flood based on past data and topography.

• Used for zoning, insurance, and emergency planning.

Dams

Store water and release it slowly. Trap sediment, harm ecosystems, risk failure.

Spillways

Channels to release excess water from dams. Can flood downstream if opened suddenly.

Levees

Embankments along rivers. Can fail catastrophically, worsen flooding downstream.

Floodwalls

Concrete walls around cities/towns. Expensive, may give false sense of security.

Channelization

Straightening/deepening rivers to move water faster.Increases downstream flooding, destroys habitats.

Zoning

Restrict building in flood-prone areas. Reduces damage long-term, but limits development.

Mass wasting

The downhill movement of rock or soil under the influence of gravity. landslides, mudflows, debris flows, and soil creep. It’s a natural process but can be worsened by human activity (construction, deforestation, road cuts).

Angle of repose

The steepest angle a slope can maintain without sliding. Depends on grain size, moisture, and friction. Steeper slopes = higher chance of movement.

Friction

Resists downhill movement. Less friction → higher landslide risk.

Gravity

Pulls materials downhill. The driving force of all mass wasting.

influences on Mass Wasting

Fluids (like water), Vegetation, Slope composition

Rockfall

Rocks break loose and fall freely. Speed: Fast

Landslide

Large block of earth moves down as a unit. Speed: Moderate/ Fast

Mudflow/Debris flow

Water + loose soil/rock move like wet cement. Speed: Fast

Soil creep

Very slow, gradual downhill movement of soil. Speed:Very slow 

What is Soil creep

Caused by freeze–thaw cycles or expansion/contraction of soil Evidence: leaning fences, tilted poles, curved tree trunks.

2014 Oso landslide

Occurred after weeks of heavy rain saturated glacial sediment. A previous slide area reactivated, collapsing into the valley. Result: 43 deaths and complete destruction of homes. Shows how water saturation + weak geology can cause deadly failures.

Subsidence

The gradual sinking of land due to removal or collapse of material underground.

Causes of Subsidence

Groundwater or oil withdraws, Underground mining, Natural dissolution of soluble rocks (like limestone → sinkholes).

Sinkholes

Form when limestone (carbonate rock) dissolves by slightly acidic groundwater.

Where are sinkholes common

karst topography regions (like much of Kentucky and Florida).

Hazard mapping

Identifies areas at risk

Slope monitoring

Instruments detect movement before collapse.

Drainage control

Reduces water infiltration and slope saturation.

Vegetation planting

Stabilizes slopes naturally.

Retaining walls and rock bolts

Physically reinforce slopes.

Avoidance

Don’t build on steep or unstable slopes!

Engineering and Safety

Engineers balance friction (resisting) vs. gravity (driving) forces. A slope is stable if friction > gravity. Building or adding water weight can tip the balance and cause failure.