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Transcript
Water, water, everywhere, And all the boards did shrink; Water, water, everywhere, Nor any drop to drink. - Samuel Taylor Coleridge The Rime of the Ancient Mariner Possible Misconceptions -Oceans are just like a huge lake, rarely moving -NO! They are CONSTANTLY moving. The waves and currents at the surfaces to the currents that are unseen underneath the surface. -The different seas and oceans are separated from each other, that’s why they have different names -NO! Look at a globe or a map, they are all connected. -The ocean is just good for swimming and has no effect on me, I live in Alberta for crying out loud! -NO! The ocean is a vast source of food (fish), petroleum products, and others used commonly such as gelatin-like products used in food. -The ocean also affects the weather and rainfall of Alberta and the rest of the world. A Sea Full of Salt -What is different between river and lake water and ocean water? -How is this measured and what is the term for this measurement? Salinity – the measurement of how salty water is 3.5% in seawater meaning 35g of dissolved salts in 1L of water (35g/L) density is 1.03g/mL on average though can get much denser up (to 1.5g/mL) freezing point is -2 degrees Celsius due to high salt content which lowers the freezing point -The main component in sea water other than water is chloride followed by sodium which is the same compound found in the salt on your table! -There are other components as well that also combine to make salts. -Where do these come from?? Sediments and minerals and salts from the land washes out into the oceans. First proposed by Sir Edmond Halley. Na also came from tectonic plates underneath seawater Cl came from underwater hydrothermal vents and volcanic activity Seawater composition H20 96% Cl 2% Na 1% Mg 0.13% other: S, Ca, K, Dead Sea in Israel - has no outlet so salt builds up in concentration - -saltiest water on Earth Other salty water Great Salt Lake, Utah, USA The Mysterious Ocean Floor -Visible light is not able to pass more than about 100m into the ocean so scientists had to develop different ways to discover what the ocean floor, or ocean basins, looked like! (More later) -There are 5 major features of the ocean floor: 1) Ocean Ridges – huge underwater mountain ranges which are the youngest parts of the ocean floor and caused by volcanic eruptions. 2) Trenches – deep, narrow, steep-sided, canyons formed where a continental plate meets an ocean plate. The opposite of an ocean ridge. 3) Abyssal Plain – found between the ridges and trenches and are formed of thick deposits of sediment from the continents. 4) Continental Shelf – part of the continent that is underwater. Exists from the coastline to the ocean basin and gradually slopes downward. 5) Continental Slope – the edge of the continental shelf that plunges rapidly to the ocean basin. How Does This Happen? -There are no rivers, wind, rain, or ice on the bottom of the ocean to erode and shape the rock. -Instead the formations are made by tectonic plate movements. -Ridges as molten lava is forced out between two plates and trenches as ocean plates move under continental plates. -Tectonic plates are constantly growing and shrinking. -Sediments that form the abyssal plains is washed into the ocean by rivers and then moves to the plains by great underwater landslides and ocean currents. -These landslides are started by earthquakes or gravity. Wonderful Waves -Waves are just ripples caused by steady ocean winds -They begin at open sea and their size depends on how fast, long and far the wind blows over the ocean. -Even where there appears to be no wind there are still small waves called swells which are caused by distant storms and winds. -ALL waves (including sound, light, microwave, ect) have 3 properties in common: 1) Height – measured from the crest to the trough 2) Wavelength- measured by the distance of one crest to the next. 3) Speed(Frequency) – measured by the time it takes for a wave to pass a particular point -Water particles move in a circular motion and stay in the relatively same position as a wave passes. -When a wave reaches the shore the trough is slowed by the friction of the beach but the crest stays the same speed thus eventually passing the trough and tumbling over. This is called a breaker. Shorelines and Beaches -Waves usually collide with the shore at an angle which causes them to move along the shoreline creating a longshore current. -These waves and currents have energy which is able to erode and pick up sediment and carry it a distance away. -The sea water is also capable of dissolving some minerals in rock. -Eventually the sediment is dropped. -Waves continue to erode the pieces of sediment into finer pieces which eventually becomes sand. -Stronger waves and more steeply-sloped shorelines cause more sediment to be washed back to sea and the opposite for weaker waves and a gentle slope. -Seaside communities value their beaches and use methods such as building sea walls, breakwaters, and jetties to prevent strong waves and longshore currents from washing away the sand. Tides http://www.montereyinstitute.org/noaa/lesson10.html -The slow rise and fall of the ocean is called a tide -Tides are controlled by the Moon’s gravitational pull. -Spring Tides are the largest tidal movements and occur when the Sun, Moon and Earth are all aligned. -Neap Tides are the smallest tidal movements and occur when the Sun and Moon are at right angles to each other. -The difference between high and low tide is called tidal range. -The Sun is further from the Earth than the moon thus it has less influence on the tides, but when they are all aligned they work together to create a bigger tidal range. When they are at right angles the Sun works against the Moon’s gravitational pull. -At high tide it may appear the volume of the ocean is increasing but it is actually only being pulled towards the one coast and away from the opposing coast. -The side of the Earth facing the Moon is affected by its gravity thus creating a bulge and pulling the water away from the sides at right angles. Water on the opposite side of the Earth that the Moon is facing also has a bulge. -Two areas of high tide means that at least two high tides and low tides per day are typical. -The tidal range is also affected by the shoreline: narrow opening then broad shoreline vs. broad opening and narrow shoreline. Currents -Broad continuous movement of the ocean water is called a current. -These currents are driven by the fairly constant wind patterns around the world. -Three factors influence the direction of winds and surface currents: 1) Uneven heating of the atmosphere – as the Earth is heated the warm air expands creating a low pressure area. Cold air, which is high pressure, moves into these areas of low pressure creating wind. 2) Rotation of the Earth – causes the Earth to move beneath the currents (wind and water) causing them to turn. Causes equatorial winds to blow from the east thus pushing ocean currents west – Trade winds. Causes polar winds to blow from the west thus pushing ocean currents east – Westerly winds. 3) The Continents – currents are forced to turn either north or south when they hit a continent. -The combination of all these factors keeps the currents circulating in a specific way. -The northern hemisphere circulates clockwise and counterclockwise in the southern hemisphere. Temperature and Currents -If you were to graph the temperature of the ocean as you moved deeper what would it look like? -There are three distinct layers: 1) Mixed Layer – wind and currents mix the water on the surface so it is all the same temperature. Relatively warm because of the Sun. 2) Thermocline – a region about 200m down where the Sun’s radiation no longer reaches resulting in a rapid temperature decline. 3) Deep Water – water remains at a constant temperature just above freezing. Warm and Cold Currents -Why is Northern Ontario so much colder than Britain when they are equally far north? -The current feeding into Hudson’s Bay and around Newfoundland and Labrador comes from Baffin Bay up past Greenland. -The current that brings water to the British Isles is called the Gulf Stream and originates from Caribbean Sea. -The temperature of the water drastically affects the climate of the area. -The currents are able to maintain their heat because water has a very high specific heat capacity. -This means that it takes a relatively long time to heat up or cool down. -The temperature of the water influences weather systems through producing wind which alters condensation and evaporation. Why is the ocean warmer at night?? -It’s not its just a trick your body is playing on you!! -This phenomena is also part of the explanation on how ocean currents and the temperature of the water affects the climate on the land. Exit Slip Time!!! 1) List three ways that the ocean affects us here in Alberta 2) How did the ocean get salty and why is it staying salty? 3) Draw and label 2 different sets of waves going 2 different frequencies 4) Explain how the black sand beach below could have been formed. (Hint it’s NOT pollution)