Earth's Hydrosphere and Oceanography

Earth's Hydrosphere

• Earth's hydrosphere is the total amount of water on the planet
• Oceanography and oceanology can be used interchangeably to describe the study of this sphere

Ocean Coverage

• Oceans cover about 70% of the Earth's surface
• Continents cover only about 30%

Submarine Geological Activity

• Most of Earth's geological activity is submarine
• Seismic activity, like earthquakes, primarily happens on the ocean floor
• Igneous activity, such as lava eruptions, mostly occurs at the bottom of the ocean
• Mountains and landslides are more common at the bottom of the ocean

Measuring Ocean Depths

• Ocean depth measurement is bathymetry, from the Greek root "bathy-" for deep
• Continental elevation measurement is hypsometry, from the Greek root "hypso-" for height
• Maps showing elevation contours are more accurately called hypsometric maps
• Sounding is an age-old bathymetric technique using weighted anchors lowered on a chain
• Depth is determined by the chain's length when the anchor hits the seabed

Fathoms

• Ocean depth is often measured in fathoms
• Fathom is derived from the length of outstretched arms
• One fathom is precisely six feet or two yards
• Fathoms should only ever be used to measure ocean depth, and not any other measurement of length

Echo Sounding

• Echo sounding is a bathymetric technique that uses sound waves
• How echo sounding works: A ship emits sound that bounces off the seabed, and a microphone detects it
• You can calculate ocean depth from the time it takes an echo to return and the speed of sound in water
• The speed of sound in water depends on temperature, pressure, and salt content

Estimating Ocean Depth

• An average speed of sound in the ocean is approximately 1500 meters/second or 1 mile/second
• Using this average speed allows for estimated ocean depth measurement
• Half the sound travel time accounts for downward and upward sound propagation
• A whale or school of fish may compromise echo sounder's accuracy
• Sonar (Sound Navigation and Ranging) emits multiple sounds and analyzes multiple echoes
• Computers help sonar systems accurately calculate ocean depth

Ocean Depth vs Continental Elevation

• Ocean depths are far deeper below sea level compared to continental elevations above sea level
• Average ocean depth is 3.7 kilometers
• Average continental elevation is 840 meters, which is less than 1 kilometer
• Max ocean depth is 11 kilometers, Challenger Deep in the Mariana Trench
• Max continental elevation is below 9 kilometers, Mount Everest in the Himalayas
• Around 5% of the ocean floor has been thoroughly mapped

Geological Oceanography

• The U.S. Navy research after WWII led to the Theory of Plate Tectonics
• The U.S. Navy keeps exploring the ocean floor to this day
• The Deep Sea Drilling Project (DSDP) began in 1968 to retrieve rocks from the ocean floor
• The Ocean Drilling Program (ODP) replaced the DSDP in 1983, drilling over two kilometers deeper than the ocean floor

JOIDES Resolution

• The Ocean Drilling Program (ODP) utilized the ship JOIDES Resolution
• JOIDES denotes Joint Oceanographic Institutions for Deep Earth Sampling
• How JOIDES Resolution drilling worked: A drill bit was lowered into the ocean piece by piece to reach the ocean floor
• After drilling, the drill was disassembled piece by piece to return to the ship

Deep Ocean Drilling Programs

• The Integrated Ocean Drilling Program (IODP) succeeded the ODP in 2003
• The mission was called the International Ocean Discovery Program (IODP) in 2013 and is still in operation
• It serves to drill over 7 kilometers below the ocean floor

Continental Margins

• Continental margins are the boundaries of continents as they meet the ocean
• All continental margins are either active or passive
• Active continental margins are defined by seismic and igneous geological activity
• Transform faults and subduction zones trigger geological activity at active continental margins
• Passive continental margins exhibit little geological activity
• Examples include the east coasts of North/South America and the west coast of Africa
• Active margins can be found on the west coasts of North/South America
• "Trench" refers to subduction zones
• Oceanic-Oceanic subduction zones result in oceanic trenches
• Oceanic-Continental subduction zones form continental trenches
• It is important to remember both continental/oceanic trenches are at the ocean's bottom

Passive Continental Margin Topography

• A passive-type extends from the continent into the ocean
• The continental shelf is a part of the continent under the ocean and is made of felsic igneous rock
• Higher sea levels cause larger shelves and vice versa
• The continental shelf teems with solar-illuminated aquatic life
• The continental slope is the seabed beyond the shelf, which slopes to further depths
• The continental rise is beyond the slope and precedes the abyss
• Abyssal plains create the ocean basin's flattest and largest parts, and is part of Earth in common with continents

Submarine Canyons and Turbidity Currents

• Submarine canyons form within the slope, carved by turbidity currents/submarine landslides rather than by rivers
• Turbidity currents consist of water and matter pulled downward by gravity
• Turbid describes anything murky, thick, disordered, and unpredictable
• Submarine canyons are built toward continents from the ocean unlike river beds
• Historical evidence for turbidity currents causing submarine canyons includes transatlantic telegraph cables broken in the early 20th century

Continental Rises and Ocean Basins/Abyssal Plains

• The continental rise is built from sliding rocks and sediments, and is called a deep sea/submarine fan
• Ocean/abyssal plains are flattest and largest, covered in mountains and sediments
• Near ridges, mountains are seamounts
• Medium-height mountains (tablemounts or guyots) halfway to continents.
• Harry Hammond Hess called them guyots for their resemblance to Princeton's Guyot Hall
• Nearest the continent, mountains are shortest, called seaknolls/abyssal hills

Plate Tectonics and Rock Ages

• Seamounts, guyots, and seaknolls support plate tectonics
• Molten rock cools near the ridges/divergent boundaries
• Plates move as seamounts get naturally degraded
• Tablemounts (guyots) result in time
• Even more time degrades guyots/tablemounts into seaknolls/abyssal hills
• Seamount rock is youngest, guyot rock middle-aged, and abyssal hill rock the oldest, which was discovered via seafloor-drilling

Ocean Basins/Abyssal Plains and Sediments

• Ocean basins/abyssal plains are flattest despite covering tons of mountains
• This results from mountains on ocean basins/abyssal plains being covered in sediments
• Rock closest to continents has sediments result in thickest rock
• Close to the ridges, the rock and sediment are thinning.
• Hills=thickest cover.

Sedimentary Rock and Marine Life

• Basins are covered in biogenic sedimentary rock
• Composition matches what lives near the ocean surface over the rock
• Microscopic sea creatures are moved far by ocean currents.
• Pellets of ocean creature excrement creates lithified biogenic sedimentary rock.

Water Molecules

• The water molecule features a single oxygen atom covalently bonded to two hydrogen atoms.
• Oxygen also has two unshared pairs of electrons.
• Molecular geometry disregards unshared pairs
• Electronic geometry includes unshared pairs
• Water's electronic geometry features a distorted tetrahedron shape
• Water molecule has negative charge on oxygen side of molecule
• Water molecule is electrically dipolar because it’s all together neutral, but one side has a positive charge and the other has a negative charge.
• Extraordinary features result from this polarity.

Water Molecules and Their Interactions

• Water molecules can both attract and repel other water molecules
• Like charges repel, and unlike charges attract
• Positively-charged hydrogen sides of water molecules repel if too close.
• Negatively-charged oxygen sides of water molecules repel if too close.
• Water molecules oppositely charge attract
• Water's cohesion refers to its ability to attract itself, resulting in surface tension
• Water also features adhesion, sticking to molecules besides it, leading to the meniscus of water and capillary action.

Chemical Reactions

• Molecules need to be in a liquid to possibly react
• Substances rarely react even in liquids without molecule disassociation
• Disassociation allows molecule cations and anions to freely bond
• All molecules set to react is collectively called the solute
• The liquid they are within is the solvent.
• Solute and solvent together makes the solution.
• Most liquids are not effective, instead requiring a good solvent quality

Solutions

• Because universal, chemists consider water the best solvent
• Water rips apart pretty much any solute, facilitating reactions

Lifeforms and Water

• All lifeforms are born, grow, move, ingest, excrete, and reproduce before dying
• All of life's actions need energy
• Brain continues to expend energy when people sleep
• All lifeforms get energy from chemical reactions needing solvents
• Water the life solvent.

Water and Heat

• All that lives composed of mostly water
• Heat capacity indicates how heat must get extract to reduce temperature or adds to increase it
• This measures how difficult the substance changes
• Water's cohesion causes large heat capacity
• Large amount of heat or extract. Stabilizes planet temperature to small difference

Day/Night and Desert Temperatures

• Daytime is warm and nighttime is cold on any planets
• Water regulates temperature due to capacity
• Extremes exist due to a scarcity of water
• Water stabilizes temperatures,
• Desert nighttime colder because lacks water

Water and Climate

• Temperature is polar
• Poles have extreme climate
• Abundant water cover moderate planet because water currents
• Continental coasts lead to milder temperatures.
• This is named the marine effect.
• Southern Hemisphere has less intense seasons because of stabilizing climate and called a water Hemisphere.
• Northern Hemisphere has more intense seasons due to land.
• This is nicknamed the land Hemisphere.
• All facts remain accurate for locations with greater and less temperatures latitude degrees.

Water and Poles

• Antarctica’s temperatures more cold
• North Poles experience marine effect
• South pole has continental effect and Antarctica surrounding.

Salt and Water

• The various salts dissolved exist in all water
• Most abundant has the Ordinary table sodium chloride NaCl-
• Ions are both positive and negative.
• Ocean collects rivers, turbidity currents, and volcanoes.
• Overall constant salt level.
• sedimentation and biological processes lower
• Salt levels.

Salinity in Water

• Saltiness refers to salinity, measured precisely as a fraction as total water
• Increases with more salt, but that reduces with greater volume
• Salinity changes water in its content.
• Fractions are review to understand. A fractional amount must understand that
• Numerator top while denominator is bottom, and the total pieces. It makes what parts exist
• Percent's are hundred pieces

Degrees of Salinity

• Some waters are more salty than other water
• Earth and Ocean roughly the same due to how we determine the range
• Higher salinity exists from 35% or less. Water or more salt is how the salinity range.

Water Types

• Hypersaline, brackish, seawater
• It could result more commonly from water than
• Brackish can result from too little. It results from the water.
• Mean Sea level shifts the water body. Glaciers and rivers affect the body. And temperatures affect too

Salinometers

• Electrical Conduction measures how one tests the salt
• The voltage is one test we all need current because high is good and low is needed
• One needs to add pure water due to test.

Ocean Interactions

• They mix due to salty or large
• If it descends, it must decrease otherwise
• If it's sea water, therefore is
• Therefore is Isohaline, with the steady part for its route
• Water must be roughly the same due to equal parts, but water could have freezing state.. Thermocline temperature must happen for the route.
• The change affects where where water is due to steep temperature due to where. There is a thermo Cline. Density causes density from one section.. the Equator and Polar change.