The Seafloor

Section 1

Seafloor geography• Continental shelf – the gradually sloping end

of a continent that extends under the ocean– Atlantic coast – 100 km – 350 km into the sea– Pacific Coast – 10 km – 30 km– Ocean depth at continental shelf – avg. 200 m

Continental slope• Extend from edge of continental shelf to the

ocean floor• Descends from 200 m to 4,000 m deep

Abyssal Plains• Sediments constantly settle on the bottom

filling in valleys creating flat seafloor called abyssal plains– Ocean depth at abyssal plain – 4,000 m to 6,000 m

• Seamounts – under-water inactive volcanic peaks

Volcanic Island• Volcano that breaches the surface of the

water forming an island

Mid-ocean Ridges• The area in an ocean basin where new ocean

floor has formed• Forms due to oceanic plates moving apart and

lava hardening

Subduction Zones• Subduction zones are marked by trenches –

long, narrow steep sided depression where one crustal plate sinks beneath another

• Mariana Trench 11 km ( 10,000 m) below sea level (deeper than Mt. Everest is tall)

Seafloor Mineral Resources• 1 - Continental Shelf – petroleum and natural gas deposits – Sand and gravel can be dredged – Rivers deposit minerals that are concentrated in

one place by ocean currents called placer deposit

• 2 - Deep Water Deposits• Hot water comes out of cracks near mid-

ocean ridges and quickly cools causing minerals to fall out• Ex: sulfur, iron, copper, silver, zinc

• Hard to mine economically b/c so deep• How would you mine them?

Section 2Life in the Ocean

Photosynthesis

• Using energy from sun to produce energy• Sun goes through water up to 100 m deep

Producers/Consumers• Producers – org. that produce their own food– ex: algae, seaweed, kelp, phytoplankton

• Algae in oceans are an important source of oxygen

• Consumers – org. that eat (consume) producers– Ex: shrimp, fish, dolphins, sharks, killer whales

Food Chain/Food Web

• Org. transfer energy from one to another• Ex:

algae copepods herring cod

seal killer whale

Chemosynthesis

• Org. such as bacteria that chemosynthesize or use sulfur to create energy

Reproduction• Corals and sponges release reproductive cells

into water for currents to distribute• Others like salmon and sea turtle return to the

same place each year to spawn or nest

Ocean Life• Most org. live above continental shelf since

most of food is located here• b/c relatively shallow & sun passes to the

bottom

Plankton• Org. that drift with the current– Ex: algae and jellyfish

• Phytoplankton – producers – plants that drift • Zooplankton – consumers – hatchlings, crabs,

diatoms

Nekton• Animals that actively swim– Ex: fish, whales

• Org. control buoyancy using air bladder• Bioluminescence – luciferin molecule – used

to attract bait, defense mechanism

Benthos• Plants/animals living on the seafloor– Ex: sea cucumber, sea urchins, flounder, sea

anemone, sponges

Beach Habitat• Sand fleas/mole crabs, worms• Makes holes in sand when water covers holes

they filter feed• Where sand is constantly covered – fish

turtles horseshoe crabs• Org. deal with lots of change

Rocky Shore Habitat• Starfish, anemones, mussels, barnacles, attach

to rocks• Tide pools area where water remains during

low tide– Good place to lay eggs b/c safe from predators

Estuary

• Area where mouth of a river opens into an ocean, lots of biological life

• Brackish water – fresh water & salt water mix• Great place for hatchlings – many plants for

protective cover and food• Important economic food source• Oysters, shrimp, clams, crab

Chesapeake Bay

• VA’s estuary• Very easy to pollute b/c

rivers flow directly in them

• Pollutants:– Pesticides, herbicides,

insecticides, oil, biosolids, fertilizers

Coral Reefs• Coral thrive in sunlit warm water• Animal build hard calcium capsules around its

body– Calcium from ocean

• Reef forms as org. connect to each other• Other animals begin to live there

Section 3Ocean Pollution

Pollution• Anything not native to the environment that

causes damage to org. by interfering w/ their life processes

• Oceans are environmentally and economically important

• Human activity have consequences for the ocean

Pollution Introduction

• 4 ways:– Deliberate dumping– Lost overboard accidentally– Air pollutants the enter through rain– Carried by rivers - runoff from lawns (herbicides),

crop fields, construction sites (sediment)

Sewage• Combined Sewage Overflow – Lynchburg• Algal blooms – caused by fertilizers, sewage

inc. amount of algae, algae dies, bacteria that decompose use up all oxygen, cause fish kills

Chemical Pollutants• Pesticides, insecticides, herbicides • Industrial waste contain heavy metals like

mercury and lead, polycarbonated biphenyls (PCBs)

• biological amplification – when harmful chemicals can build up in the tissues of organisms that are at the top of the food chain

Oil• Mostly from runoff of streets, parking lots,

dumped into drains/ground• Oil spills – use bacteria that eat oil and change

its chemical composition called bioremediation

Solid Waste• Balloons, plastic bags sea turtles eat mistaken

for jellyfish• Biohazardous waste – needles can make

beaches unsafe

Sediment• Forestry, construction, agriculture not

practicing good erosion control techniques• Sediment covers coral reefs & fill estuaries

Bathymetric Maps

• Isobaths – contour lines used to measure areas of equal depth