Grade 8 Science - Unit 1 Water Systems Chapter 2 - PDF

Grade 8 Science Unit 1 – Water Systems Chapter 2 Notes Ocean Basins  a low spot in Earth’s surface that is surrounded by high land and which has filled with water, can accumulate over millions of years. 5 Major Oceans from Larges...

Grade 8 Science Unit 1 – Water Systems Chapter 2 Notes Ocean Basins  a low spot in Earth’s surface that is surrounded by high land and which has filled with water, can accumulate over millions of years. 5 Major Oceans from Largest to Smallest: 1. Pacific 2. Atlantic 3. Indian 4. Southern 5. Arctic How were the Oceans first formed? 1. Volcanic Action  Water inside volcanic materials was released into the atmosphere in the form of water vapor.  As it cooled it condensed and fell back to the earth where it flowed downhill into the ocean basins. 2. Plate Tectonics  At one time the Earth was one large super continent called Pangea.  As the tectonic plates drifted apart the large ocean was separated by the continents into the oceans we have today. 3. Erosion  The breakdown and movement of rock material has been constantly working to form the large ocean basins. 4. Glaciation  Glaciers have their main role as a force of erosion in developing continental drainage systems as they cut their way across the landscape during the several ice ages. 1|Chapter 2 – Sci8 Labelling the Ocean Floor A B D C E A: Continental Shelf:  the submerged part of the continent closes to the shore. Slopes gradually away.  The widest continental shelf in the world is off Newfoundland’s East coast, called the Grand Banks. B: Continental Slope  At the edge of the shelf this slope goes down at a steep angle to the sea floor.  At the bottom of the slope is the abyssal plain. C: Abyssal Plain  The flat areas in the deep sea. D: Ocean Ridges  Long undersea mountain ranges caused by magma from the Earth’s hot core oozes up and quickly hardens.  This occurs when two tectonic plates are pushed apart.  The largest oceanic ridge is the Mid-Atlantic Ridge in the Atlantic Ocean. E: Ocean Trench  Forms when tectonic plates collide.  The deepest trench is known as the Mariana’s Trench and is deep enough to submerge an object as tall as Mount Everest. 2|Chapter 2 – Sci8 How do we explore the Ocean Floor? 1. Sonar  Uses sound waves to probe the seabed. - sound waves are sent out and reflect back from the ocean bottom giving an idea about the depth at different points. 2. Satellites  Can survey large areas of ocean in a relatively short time. - able to record and transmit data in all kinds of weather day and night. - can receive information from buoys anchored to the ocean floor. 3. Core Sampling  taking samples of the ocean floor directly for analysis of the layers of rocks that exist to learn more about it. 4. Underwater photography/videography  New deep sea cameras and video allow pictures and video to be taken 6000m beneath the surface. 5. Deep Sea submersibles  These have given us the most detailed information we have about the deepest parts of the ocean. - These are small but extremely strong vehicles capable of travelling to great depths. 6. Diving  physically diving into the water to learn about the ocean floor. - Limited depths due to high pressures. 3|Chapter 2 – Sci8 Ocean Currents Current – a large amount of ocean water that moves in a particular and unchanging direction. - There are more than 20 major ocean currents in the world. - Can be affected by wind (surface currents) or temperature and density (deep water currents). Local Ocean Currents: 1. Labrador Current (cold water) 2. Gulf Stream (warm water)  the Gulf stream starts around the equator where the Sun heats up the water.  It carries the warm water from the tropics past Newfoundland making the Grand Banks one of the worlds richest resource areas.  The warm water then mixes with the cold water from the Labrador current.  This creates an ideal location for nutrients and also affects NL’s climate. The mixing of the Gulf Stream (warm) and Labrador Current (cold) creates NL’s climate in two ways: 1. It generates heavy fog 2. It creates large temperature fluctuations Ocean Waves - Large ripples in the ocean caused by winds. - There is an uneven heating of the air, which causes a difference in air pressure. This difference causes movements in air (wind) - The energy in the air is transferred to the water. Types of Waves: 1. Swell  steady movement of smooth waves on a calm day. 2. Breaker  As waves approach a shoreline the wavelength decreases and height increases. - when it reaches the shore the wave collapses onshore in a tumble of water as the crest of the wave outruns the trough. 3. Tsunami  Large waves that can be set in motion by earthquakes on the ocean floor, landslides or volcanic eruptions near the shoreline. Ex: Tsunami hit the south coast of Newfoundland in 1929. 4|Chapter 2 – Sci8 Wave Features 1. Crest  highest part of the wave. 2. Trough  lowest part of the wave. 3. Amplitude  measured from the rest position to the crest or the rest position to the trough. 4. Wavelength  the distance from one crest to the next. Wave Interactions with Shorelines: - As rocks are rubbed against each other in surging water, rock fragments are smoothed and ground down into smaller pebbles and grains of sand. - The energy of the wave causes shorelines to erode and sediments to be deposited on the shore. - Tides work together with waves to shape the shoreline. Weathering  the breakdown of rocks into smaller particles Erosion  the movement of those weathered particles. Deposition  when eroded material is dropped or left behind. 5|Chapter 2 – Sci8 Effect of waves on shorelines depend on: 1. Slope of the shoreline 2. Shape of the shoreline 3. Wave Energy 4. Type of rock material Can create: 1. Sandy Beaches  Formed on a shoreline with a gentler slope and calm waters, smaller rock fragments can settle and build up, forming a beach.  Sandstone is a softer material and will erode at a faster rate than shale since shale is harder rock. 2. Shoal  Also called a sandbar  Develop where a stream, river or ocean current promotes deposition of sediment and sand, resulting in shallowing or shoaling of the water.  When surface waves move toward shallow water, such as a beach, they slow down, their wave height increases and the wavelength decreases. This is called shoaling. 3. Rocky Beaches  Along steeply sloping shorelines, these rock fragments are washed back into the sea. This leaves a shoreline of bare rock, boulders and larger stones. 4. Headlands and Bays  A bay is located between two headlands. Wave energy is concentrated on headlands and spreads out as it reaches bays.  The high energy of the wave on the headlands cause erosion and create structures like sea caves, sea arches and sea stacks. 5. Sea Caves  When waves erode a cave in the boulders and rock. 6. Sea Arches  When caves increase in size and meet an arch can be formed. 7. Sea Stack  When erosion causes a piece of rocky land to be cut off from the rest of the land. 6|Chapter 2 – Sci8 Ocean Tide - The daily cycle of the ocean water rising and falling. - The upper and lower edges of a beach are determined by the high tide and low tide. Tidal Range  the difference in level between the high tide and the low tide. What causes Tides? - The cycle of tidal movement is caused mostly by the Moon. - The gravitational pull of the Sun and the Moon on the ocean cause tides. Spring Tides - Happen when the Earth, the Moon and the Sun are in a line. - Have the highest tidal range: low tides are really low and high tides are really high. Neap Tides - Happen when the Sun and Moon are at right angles to each other. - Have the smallest tidal range; there is very little difference between the size of the high and low tide. 7|Chapter 2 – Sci8