Presentation on theme: "Section 4. Erosional Problems America's Pacific Coast Narrow beaches with steep cliffs and mountain ranges Problems come from the changing of natural."— Presentation transcript:
Erosional Problems America's Pacific Coast Narrow beaches with steep cliffs and mountain ranges Problems come from the changing of natural systems by humans. Big Problem: Beaches are becoming more narrow. o Sand supplied by rivers. o Dams stop the sand from coming to the beaches. o Sand protects cliffs from waves. o Without the extra sand, cliffs are experiencing quicker erosion. Erosion changes by year depending on storms. If the sea levels rise, more shoreline erosion is to occur. Shoreline Erosion
Erosional Problems Atlantic Coast Wider beaches than the Pacific coast. Followed by dunes and lagoons. Barrier islands: A low, elongate ridge of sand that parallels the coast. o Additional sand makes barrier islands more common for development. Developing faster than barrier islands can handle. o Receive full brunt from ocean during storms.
Classification based upon sea level changes Two types of coasts o Emergent coasts - develop because of of area uplift or a drop of sea level o Exhibit specific landforms Wave-cut cliffs - erosion causes cliffs to crumble and retreat Marine terrace - Wave-cut platform that is uplifted above sea level by tectonic forces and exhibits a seaward-sloping shape Shoreline Types
Classification based upon sea level changes Two types of coasts o Submergent coasts - created when sea level rises or the land adjacent to the sea subsides o Exhibit estuaries Estuaries - drowned river mouths Shoreline Types
Tide- Daily change in the elevation of the ocean surface The easiest ocean movements to observe other than waves Caused by the gravitational attraction exerted upon Earth by the Moon and, to a lesser extent, by the Sun Tidal bulge- the Moon's gravitational force causes water to bulge on the sides of Earth nearest and directly opposite to the Moon The tidal bulges remain in place while Earth rotates "through" them and causes high and low tides Most places on Earth experience two high tides and two low tides each day Tides
S pring tide- highest tidal range that occurs near the times of the new and full moons, when the Sun, Earth, and Moon are aligned Neap tide- lowest tidal range, occurring near the times of the first- and third-quarter phases of the moon Every month, there are two spring tides and two neap tides, each about one week apart Tides
There are three types of tidal patterns *Diurnal Tidal Pattern -Characterized by Single high tide and single low tide each tidal day. Ex. Northern Shore of Gulf of Mexico *Semidiurnal Tidal Pattern -Characterized by Two high tides at the same height and two low tides at the same height each tidal day. Ex. Along the Atlantic Coast of the United States of America Tidal Patterns
*Mixed Tidal Pattern -Characterized by Two high tides and two low tides each tidal day. Unlike semidiurnal mixed tidal patterns the heights of the high tides differ greatly as well as the low tides. Ex. The Pacific coast of the United States of America Semidiurnal Mixed Diurnal
Tidal current horizontal flow of water accompanying the rise and fall of tides induced by tidal forces currents advancing into coastal zones make flood currents currents moving out to sea make ebb currents Tidal flats Areas affected by slack water (alternating ebb and flood currents) tidal flats vary from long, narrow stips seaward of the beach to zones extending for several km, depending on their nature.
Tidal delta Deposit of sediments due to tidal currents May develop inland of an inlet as a flood delta or seaward of an inlet as an ebb delta flood deltas are more common and more prominent that ebb deltas.
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