OCEAN AND CURRENTS Flashcards
Surface current is also known as
Ekman layer
Gyres
The loops of ocean currents
Help re-distribute heat (warmth)
Coriolis effect
The loops of ocean currents which rotate clockwise above equator and anticlockwise below equator due to the earth rotation, which is anticlockwise
Water at pole is dense
Water at pole is dense because it is cold and it has high salt quantity since water crystallises leaving behind salt, cold water is denser
Thermohaline circulation
Since cold water is denser, it sinks down and warmer surface water takes its place setting a vertical current called thermohaline circulation
Global conveyor belt
Thermohaline circulation (deep water) + wind driven currents (surface)
Two external forces that influence world ocean generating currents
Gravitation
Energy flux from sun
What does low pressure area result in?
Low pressure areas result in higher temperature, therefore resulting in higher rainfall
What does high-pressure area result in?
High-pressure area results in lower temperature as a result, lesser rainfall
Global circulation can be divided into
Three cells
1. Hadley cell.
2. Ferrel cell.
3. Polar cell.
NOAA
National oceanic and atmospheric administration
What is density of pure water?
1000 kg/m3
Or
1g/cm3
Conductivity
Can be determined from the amount of salt content
Since electric current passes more easily in salt containing water
How is depth calculated?
Pressure is recorded in decibars, which is converted into depth (m), using a strain gauge pressure monitor, or other pressure calculating instruments.
Thermistor
Thermal + resistor
If temperature is low, resistance is high, therefore less current will pass
If temperature is high, resistance will be low, therefore, more current will pass
Temperature is inversely proportional to resistance
The global salinity budget
It consists of
1. Output (removal of salt) eg. melting glaciers, addition of freshwater bodies, etc.
2. Input (sources of salt) eg. run off from land, openings in the sea floor due to volcanoes and hydrothermal vents, etc.
3. Distribution (mixing)
Wind
Horizontal movement of air with respect to earth surface
Instrument to measure speed of wind
Anemometers
Instrument used to measure direction of wind
Wind vane
Factors affecting wind
- Coriolis effect
- Pressure gradient force
- Frictional force
Classification of wind
- Permanent/primary/planetary
- Seasonal/secondary
- Local/tertiary
Permanent wind
Blow from high-pressure belt to low pressure belt constantly
In the same direction
Throughout the year
Blow over continents, seas, and oceans
Types - tradewinds, westerlies, easterlies (polar)
Secondary or seasonal winds
Change their direction periodically with change in seasons
Example, monsoon went
Local winds
Sea breeze and land breeze
Valley and mountain breeze
Hot wind and cold wind
Classification of surface waves based on causative forces
- Wind generated.
- Swell waves.
- Seismic waves.
- Seiches
- Storm surges
Wind generated wave
- Capillary waves.
- Small, and short ; <1.73cm
- Generated by light winds or disturbances - Gravity wave.
- >1.73 cm
- Generated by stronger winds
- Gravity is the primary restoring force
Swell waves
Travel out of their area of origin
Generated by distant Weather systems and can travel vast distances
Seismic waves
(Tsunamis)
Generated by underwater earthquakes, volcanic eruption or landslides
Has higher wavelength
Seiches
- standing waves that form in enclosed or partially enclosed, water bodies like bays, lakes, harbours
- caused by atmospheric pressure changes, seismic activity, or tidal forces
Storm surges
(Hurricanes)
Long wave generated by strong onshore winds or low pressure
Meterological instruments
- Thermometer - measures, air temperature ; types include mercury, alcohol, digital
- Barometer- measure pressure ; types include mercury, digital, aneroid
- Hygrometer- measures humidity ; types include digital, hair, psychrometers
- Anemometers- measures, wind speed; types include cup, vane, ultrasonic
- Wind vane - measures, direction of wind.
- Rain gauge - measures, amount of precipitation; types include acoustic, standard, tipping bucket, weighing
- Ceilometer - measures, height of cloud base and overall cloud cover.
- Pyranometer - measures solar radiation.
- Snow gauge - measures, amount of snowfall.
- Radiosonde - measures upper atmosphere’s temperature, pressure, and humidity.
Stevenson screen
Shelter that houses meteorological instruments and protects them
Composition of atmosphere
Nitrogen 78%
Oxygen, 21%
Argon 0.9%
Carbon dioxide 0.04%
Water vapour 1%
Ozone and dust particles in trace amounts
Structure of atmosphere includes
Troposphere
Tropopause
Stratosphere
Stratopause
Mesosphere
Thermosphere
Exosphere
Troposphere
Lower most layer
Height is 8 km at pole and 18 km at equator
Climatic and weather changes takes place here
As you go higher in troposphere, temperature decreases
Tropopause
Constant temperature zone, separating troposphere and stratosphere
Stratosphere
Second layer of atmosphere
Height is up to 50 km
Contains ozone layer
Aeroplanes fly here to avoid weather interference
As you go higher in stratosphere, temperature increases
Stratopause
Constant temperature zone that Separates stratosphere and mesosphere
Mesosphere
Third layer
Height is up to 80 km
Meteorites burn in this layer on entering Earth’s atmosphere
As you go higher in mesosphere, the temperature decreases
Mesopause
Constant temperature zone that separates mesosphere and thermosphere
Thermosphere
Ionosphere lies within thermosphere
Ionosphere contains electrically charged ions
As you go higher in thermosphere, the temperature increases
Satellites orbit in the upper part of thermosphere
Exosphere
Upper most layer
Merges with open space
Ozone
Highly reactive
Allotropic molecular form of oxygen
containing three atoms of oxygen
At ground level gives a pungent acidic odour (similar to chlorine)
Density = 2.14kg/m3
Molecular weight = 48 g/ mol
Boiling point = -112 degree Celsius
Melting point = -192.2 degree Celsius
There are two types of ozone, natural and man-made
Natural ozone is found in the stratosphere, which is known as these stratospheric ozone, which is created due to interaction between UV and oxygen
Man-made ozone is found in the troposphere which is called as tropospheric or ground level. Ozone formed primarily by photochemical reaction between volatile organic compounds and nitrogen oxides.
Ozone + water =
O3 + 3H2O = 3H2O2 (hydrogen peroxide)
Carbon dioxide
Colourless
Odourless
Gas
Molar mass = 44 g/mol
Melting point = -56.6°C
Boiling point = -78.5°C
Carbon dioxide + water =
CO2 + H2O = H2CO3 (carbonic acid)
What are the seven primary greenhouse gases?
Carbon dioxide CO2
Methane CH4
Nitrous oxide N2O
Hydro fluorocarbons HFCs
Per fluorochemicals PFCs
Sulphur hexa fluoride SF6
Nitrogen trifluoride NF3
Marine transgression
Geotic event during which sea level rises relative to land and results in flooding
Reasons can be land sinking, or ice, melting, et cetera
Marine regression
Geologic process in which area of submerged sea floor are exposed above sea level
Opposite to transgression
Marine ingression
A coastline shaped by penetration of the sea as a result of crustal movements
Plate tectonic
Movement of large pieces of earth’s crust called tectonic plates
Sea floor spreading
Proposed by American geophysicist Harry H. Hess in 1960.
It is a process of magma Welling up in the rift as the old crust pulls itself in opposite directions called seawater cools the magma which creates new crust
Uniformitarianism
Popularised by Charles Lyell in 19th century
It suggests that the same geological processes and natural laws that operate today have been operating throughout earth history and that can be used to explain geological features and formations found in the past
Continental drift
Proposed by Alfred wegener in 1912
Accordingly, there was one super continent Pangaea and one mega ocean Panthalassa which later divided into Laurasia and Gondwanaland
What is the evidence for continental drift?
Apparent fit of continents
Fossil correlation
Rock and mountain correlation
Paleoclimate data
Glacial evidence and coal
Oil pool and oil traps
Sub surface accumulation of oil
Dead remains of plants and animals sink on the ocean floor, where under high-pressure and temperature after centuries, they get transformed into hydrocarbons like natural gas and liquid oil
They move from source rock, where they were formed and migrate to Reservoir rock where they are found by us . Since oil and gas are lighter than water, they tend to rise upwards through pores or any permeable rock formation. Thus, the poor or permeable rock is the reservoir rock.
Some rocks are non-permeable and the strap, the oil and gases, which is called as oil trap
Types of oil trap
- Structural trap.
- rock layers are deformed /displaced due to tectonic forces (folding/faulting) - Salt Dome trap.
- Large salt mass rises due to low density and plasticity, which sees the pores and permeable rock with oil and gases, and hence traps them - Stratigraphic trap.
- Due to changes in composition of rock layers
How do we find oil traps?
Seismic, gravity, magnetic survey, well logging, core sampling, et cetera
Stress
Quantity of force causing deformation
Measured in Pascal
One Pascal is equal to 1 Newton per metre square
Normal stress
Perpendicular to the surface
Tensile stress
Pulling in outward direction for object to stretch
Compressive stress
Stress is in the inward direction, which causes the object to squeeze/compress
Shear stress
Parallel to the surface
Strain
Experience enough stress to deform and change the shape or volume of the object
It is unit less
Building blocks of rocks are
Minerals
What will happen to the rock if temperature and pressure is high?
Rocks, strength, and viscosity will decrease, making it weaker for deformation
Viscous deformation
Deformation of fluids, example lava
Brittle deformation
Most surface rocks are brittle on applying stress, hence called brittle regime
Elastic deformation
If stress is too much, there is a fracture
one such reason of earthquake
Atomic bonds, bend and accumulate energy like rubber band
Incompetent rocks
Weak and soft
Competent rocks
Hard and strong
Subduction zone
Known for massive earthquake
As the oceanic crust sub duct down there, the temperature and pressure is high at greater depth where presence of competent rocks are found . What is the result of elastic deformation of the rocks, the atomic bonds bend and accumulate energy on too much stress there is a fracture which results in earthquakes
Hence, we expect the largest earthquakes to occur in the hardest and most competent rocks, which is the oceanic crust below the continental crust .
Plastic deformation
Bonds break, therefore, there is no accumulation of energy, hence rock Bends
Cyclones are found in
South Pacific and Indian Ocean
Hurricanes are found in
Eastern Pacific, Central Pacific and North Atlantic
Typhoons are found in
North West Pacific
