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Unformatted text preview: 1 1 • Distribution of sediments on the sea Distribution of sediments on the sea floor floor • Seabed Resources Seabed Resources Sediments are particles of organic or inorganic matte that accumulate in a loose, unconsolidated form. Record of geologic/oceanographic history • Types (Classification) Types (Classification) • Location or distribution of sediments Location or distribution of sediments • Rates of Deposits/Accumulation Rates of Deposits/Accumulation Chapter 5 Chapter 5 - Sediments Sediments 2 1. Sediments and volcanism are the most important agents of physical change on the deep-ocean floor 2. Study of sediments is important to ocean’s chemistry, morphology and history as well as to Earth’s climate (paleoclimate) The position and nature of sediments provide important clues to Earth's recent history, and valuable resources can sometimes be recovered from them. The ages of portions of the ocean floor can be determined by studying core samples of sediments just above the basalt seabed, (see Fig. 5.26 for an example). The youngest sediments are found near the ridges and rises and the oldest close to the trenches. Study of Sediments is important to oceanography because: 3 Sediment Classification Sediment Classification • Particle Size (Grain Size) Particle Size (Grain Size) • Location (where the grains are deposited) Location (where the grains are deposited) • Source and Chemistry Source and Chemistry 4 Large (L) Medium (M) Small (S) Grain Size Classification Grain Size Classification 5 Sediments May Be Classified By Particle Size Sediments May Be Classified By Particle Size The velocities of currents The velocities of currents required for erosion, required for erosion, transportation, and transportation, and deposition deposition (sedimentation) of (sedimentation) of sediment particles of sediment particles of different sizes. different sizes. To dislodge and carry a To dislodge and carry a particle of size A, the particle of size A, the speed of a current must speed of a current must exceed 20 centimeters exceed 20 centimeters per second (8 inches per per second (8 inches per second). When the second). When the current falls below 1 current falls below 1 centimeter per second centimeter per second (1/2 inch per second), (1/2 inch per second), the particle will be the particle will be deposited. deposited. 6 Sediment can be classified by particle size. Waves and currents generally transport smaller particles farther than larger particles. How far sediments go horizontally and how long it takes to get to bottom of sea depends on size. Shape is also important to how sediments go around and settle in the bottom. L M S 2 7 Poorly Sorted Poorly Sorted Well Sorted Well Sorted well sorted: uniform grain size poorly sorted: variable grain size 8 Sediment Size Classification Wentworth grain-size scale (Wentworth, 1922)....
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This note was uploaded on 07/18/2011 for the course EARTH SCIE 180 taught by Professor Frankbuonaiuto during the Spring '11 term at CUNY Hunter.
- Spring '11