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Transcript
The Ocean Bottom Marine Science Pg 23 in Notebook Review 3 layers of earth Core Mantle Crust Rock Cycle Igneous Rock Sedimentary Rock Metamorphic Rock Continental Drift Plate tectonics Sea floor Spreading HMS Challenger: 1872-1876 The beginning of systemtic observations of the ocean & ocean floor HMS Challenger: 1872-1876 The beginning of systemtic observations of the ocean & ocean floor Sir John Murray (1841-1914) gave detailed account of deep sea sediments recovered during the HMS Challenger expedition. Sediments and Sedimentary Rock Make up 8% of the Earths crust 75% of the Earths surface Types of Sediments Terrigenic sediment produced by the break down of rocks on land Biogenic sediment produced by organisms Authigenic sediment produced in place by chemical reactions in seawater or within the upper sediment Volcanogenic sediment produced from the eject of volcanic eruptions Cosmogenic sediments produced from cosmic debris that constantly bombards the Earth Terrigenic Sediment Terrigenic sediment is the sand, silt, and clay you normally think of as sediment. Quartz (SiO2 crystall, “Silica”) is the dominant mineral in terrigenic sediment. Terrigenic Sediment Types of Sediments Terrigenic sediment produced by the break down of rocks on land Biogenic sediment produced by organisms Authigenic sediment produced in place by chemical reactions in seawater or within the upper sediment Volcanogenic sediment produced from the eject of volcanic eruptions Cosmogenic sediments produced from cosmic debris that constantly bombards the Earth Biogenic Sediment macroscopic: bones, teeth, shells of larger organisms rare microscopic: shells and skeletons of planktonic organisms chief producers are algae (plants, photosynthesizing) protozoans abundant CaCO3 producers: Coccolithophores 20 mm 20 mm CaCO3 producers: Foraminifera 50 mm ~400 mm Types of Sediments Terrigenic sediment produced by the break down of rocks on land Biogenic sediment produced by organisms Authigenic sediment produced in place by chemical reactions in seawater or within the upper sediment Volcanogenic sediment produced from the eject of volcanic eruptions Cosmogenic sediments produced from cosmic debris that constantly bombards the Earth Authigenic Sediments derived from dissolved material in sea water • • • • • Manganese Nodules Evaporites Phosphates Carbonates Metal Sulfides Types of Sediments Terrigenic sediment produced by the break down of rocks on land Biogenic sediment produced by organisms Authigenic sediment produced in place by chemical reactions in seawater or within the upper sediment Volcanogenic sediment produced from the ejections of volcanic eruptions Cosmogenic sediments produced from cosmic debris that constantly bombards the Earth Cosmogenic Sediments • derived from extraterrestrial sources • macroscopic: • meteor debris • rare • microscopic: • space dust (spherules, tektites) • constantly raining on Earth Spherule Distribution of Sediments Ten times more terrigenic than biogenic sediment arrives at the seafloor each year. If this sediment was distributed evenly, then terrigenic sediment would dominate the sediment cover of the seafloor. This is not the case because of most of the terrigenic material is trapped along continental margins. © The Open University © The Open University Importance of Sediments Economic Value Oil, fossil fuels Salt & Phosphorus deposits Determine shape & structure of Ocean bottom Strongly affect distribution of Benthic Organisms Chronological record of Earth’s history Tectonic history Climate history Evolutionary history Sediment Thickness 500 20 000 Continental Shelf/ Slope CLCS/11, Fig. 8.1 Law of Superposition Younger sediments over Old sediments YOUNG ---------------------OLD Sediment Classification By Grain Size By Origin Sediment Classification Grain Size Clay Silt Sand Gravel <4 μm 4-62 μm 62-2000 μm >2000 μm Table 3.1 Sediment Classification based on size Sediments are often mixtures of various grain sizes ! Ternary diagram with gravel Seamount Ocean bottom mountains Oceanic trenches