ENVS 101 1st Edition Lecture 16 Outline of Last Lecture I. GlaciersII. Glacial erosion and DepositionIII. Glaciations and Sea IceOutline of Current Lecture II. Ocean Basins and Ocean WaterIII. Ocean CirculationCurrent LectureThe ocean and the interactions it has with society: The world marine fish catch is over 80 milliontons per year. Coastal sedimentary rocks host productive oil-bearing deposits as well.Ocean Basins/Water: Seawater covers 70.8% of Earth’s surface. The remaining 30% or so of most land area on Earth is located in the Northern Hemisphere.“World Ocean” consists of water mostly found in the Pacific, Atlantic, and Indian Oceans. The Southern Ocean is the connecting point between all of the other oceans found on Earth.Answering the Question: How deep is the Ocean? Prior to the 20th century, not much was known about the depth of the ocean.- During the 1920s however, echo sounders began to be used, and the depth of the seafloor measured by how long it took for the echo to return to the boat. As sound travels through the water, when reaching a surface, sound will “bounce back” up the original source of the sound. Today, seafloor maps are made with satellites.The Mariana Trench near Guam is the greatest ocean depth measured at 10,925mThe average depth of the sea is 3970 m, and the average height of land above sea level is 840 meters. Mid-Ocean ridges form Earth’s longest mountain ridges. To put this into better perspective, if Mount Everest were to be put into the Mariana trench, it would not show above the trench, but rather still be 2-3 kilometers down from the top surface of the trench!- The oldest sedimentary rocks are over 4 billion years old. Oxygen isotopes in zircons suggest that the ocean may be approximately 4.4 billion years old. Compare this to the Earth, which is approximately 4.5-4.6 billion years old.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Where the water came from is still uncertain, a question of science. Carbonaceous chondrites, which is a type of meteorite, is characterized by its water content, filled with hydrous minerals. Several of these accereted during the formation of the Earth. In fact, a series of icy comets bombarded early Earth, bringing with them frozen water.Compare the following: Asteroids orbit the Sun (between Mars and Jupiter). The majority of Asteroids are dry, rocky objects. Meteors burn up from the friction that occurs with the Earth’s atmosphere. There are also meteorites, which are objects that survive and maintain their solid core. Meteorites are able to impact the surface of the Earth. Comets are icy, and come from beyond Neptune. Comets also have a limited lifespan, as they can only pass in close proximity to the Sun so many times before the Sun melts them away in their entirety. Another characteristic of comets is that their tails point away from the Sun.- Biotic zones include the following: The Pelagic Zone consists of plants and animals livingin the uppermost water. Plants need access to sunlight (found in the photic zone)- Benthonic organisms live on or within the bottom sediment. In a microscopic view, theses organisms look like very small sea-shells, yet are invisible to the naked eye. Whenthese organisms die, the sink to the bottom of the ocean to form sediments. Oceanic sediment is dominated by skeletal remains of single celled planktonic and benthonic animals, when more than 30% of bottom sediment consists of these remains it is called:Calcareous ooze, which is carbonate based, or siliceous ooze, which is silica based. Lithic sediment consists of rock fragments, and mantles.Ocean Salinity: Dissolved salts make up about 3.3 to 3.7% of average seawater or 33 to 37 0/00 (per mil). The totality of the oceans salt contents would make a layer of salt about 56 meters deep on the ocean seafloor. - Salinity variations are related to: Evaporation, the precipitation of rain and snow, the inflow of fresh river water, and the freezing of sea ice. Freshwater sources/ water with low salinity will typically be found in cooler zones, where less evaporation is going on in the environment, and thus cause lower salinity than in climate zones with warmer temperatures.Throughout the oceans of the Earth, temperatures are not evenly distributed, contributing to the variations in the levels of salinity. The ocean has a high heat capacity. For a given amount of heat, water has a lower rise in temperature than land. The oceans have low total and seasonal temperature range. Ocean temperatures also affect the climate over ocean and land. This in turn controls distribution of plants and animals.- Climate is also unevenly distributed, and if temperature changes in the polar regions andtropical regions are compared, since the seasonal temperature changes have much greater variation in the polar regions, temperature has larger fluctuations throughout the year. By contrast, changes in tropical regions may only vary be a couple of degrees, because there is nearly no significant temperature fluctuations, regardless of what season it is.- In terms of density: The coldest, saltiest parts of the ocean end up at the bottom because they are the most dense.- Physical Properties of Seawater vary with depth: the ocean is vertically stratified.Seawater will become more dense as temperature decreases and as salinity increases.Gravity also pulls more dense water downwards, and drives deep ocean circulation.Ocean Circulation: Surface ocean currents are broad, slow drifts of surface water caused by friction between the ocean and air flowing over it. It is typically 50-100 meters deep, and solar radiation provides heat energy, non-uniform heating generates winds, which drive the movement of surface ocean water.Each major ocean current is part of a large sub circular current system called a