Chapter 20 Coastlines and Ocean Basins. About Coastlines and Ocean Basins Coastal processes are the interaction of the climate system and the solar system. Waves and tides are key processes at the coastline. The ocean basin contains features like mountains, valleys, and volcanoes.
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About Coastlines and Ocean Basins • Coastal processes are the interaction of the climate system and the solar system. • Waves and tides are key processes at the coastline. • The ocean basin contains features like mountains, valleys, and volcanoes.
Lecture Outline • How ocean basins differ from continents • 2. Coastal processes • 3. The shaping of shorelines • 4. Continental margins • 5. Topography of the deep sea floor • 6. Ocean sedimentation
How Ocean Basins Differ • from Continents ● Lack of fragmentation processes ● slow chemical weathering ● Limited tectonic activity ● mid-ocean ridges and subduction zones ● Oceans dominated by volcanism and sedimentation
2. Coastal Processes ● Wave motion – key to shoreline dynamics ● Wind waves: depends on wind speed, duration, and distance
2. Coastal Processes ● Longshore currents (parallel to shore) ● caused by wave approach at an angle to the shore ●zig-zag path of swash and backwash occurs at the shore ●Rip currents (perpendicular to shore)
3. The Shaping of Shorelines ● Sand budget of the beach ● incessant movement ●input and output (erosion and sedimentation) ●changing conditions lead to growth or shrinkage
3. The Shaping of Shorelines ● Erosional coastal forms ● sea cliffs and wave-cut terraces ●Depositional coastal forms ●barrier islands and spits
3. The Shaping of Shorelines ● Shoreline erosion and deposition ● uplift / subsidence ●nature of rocks or sediments ●changes in sea level ● average storm wave heights ● heights of tides
2. Coastal Processes ● The tides: gravitational origin ● solar tides ●lunar tides: spring and neap
5. Topography of the Deep Sea Floor ● How we know about the deep ● Deep Sea Drilling Project ●Ocean Drilling Program ●ship-towed instruments ● deep-diving submarines ● satellite charting of seafloor
5. Topography of the Deep Sea Floor ● Important features ● mid-ocean ridges ●volcanic tracks of hot spots ●deep sea trenches ● island arcs ● continental margins
About Glaciers and the Work of Ice • Glacial erosion creates an enormous amount of sedimentary debris. • Ice covers only 10% of Earth now, but 21,000 years ago, the coverage was 30%. • The landscapes of vast areas of many continents have been sculpted by the flow of ice in glaciers.
Lecture Outline • Ice as a rock • 2. How glaciers form • 3. How glaciers move • 4. Glacial landscapes • 5. Glacial cycles and climate change
1. Ice as a Rock ● Could be viewed as any kind of rock ● igneous – formed from a liquid ● sedimentary – formed in layers ● metamorphic – transformed by pressure and recrystallization
1. Ice as a Rock ● Formation of glacial ice ● falls as snow and ice ● recrystallizes over time to ice ● with pressure of overlying ice, ice under pressure starts to flow like a very viscous fluid
1. Ice as a Rock ● Peculiar properties of the rock ice ● freezes at very low temperature compared to other rocks ● ice is less dense than the liquid it comes from (water)
1. Ice as a Rock ● Types of glaciers ● valley glaciers (alpine glaciers) ● continental glaciers (ice sheets) ● ice shelves and ice caps
