Processes That Shape Ocean Basins Continental Drainage Ocean

Processes That Shape Ocean Basins & Continental Drainage

Ocean Basins • ‘Oceans In Motion’ video • 10: 40 – 21: 20 • Describe the geography of the ocean floor • Where did the water come from? • Where did the salt in the ocean come from? • Name some of the features found on the ocean floor. • Is the ocean floor changing? Why or why not?

• Shaped by the movements of tectonic plates – Are not fixed in place • Float over a layer of molten rock • Moving very slowly due to convection currents within the Earth – Plates can converge, diverge or shear

• Features – Continental shelves • Shallow areas around the edges of continents • Composed of mainly sedimentary deposits – Volcanic Islands & Seamounts (underwater volcanoes) – Ridges • Plates slowly converge • Allows molten rock to rise up from interior and harden • Results in spreading of sea floor – Trenches • Formed where plates diverge or subduct

Glaciers • What are glaciers? • How do glaciers form? • How do glaciers change the landscape?

• Large moving bodies of ice • Continental glaciers (icecaps) – Cover large area of land • Ex. Antarctica • Valley glaciers – Glaciers that flow through high valleys between mountain peaks • Ex. Columbia Ice Fields

• Movement – Is dependent on climate – Advancing • Overall increase in size or area • Forward movement • Occurs when. . . ? – Snowfall accumulates and is compressed

– Retreating • Overall decrease in size or area • Backwards movement • Occurs when. . . ? – Snow melts faster than it accumulates

1981 1938 2009 1998

• Effect on Landscape – During the last ice age, glaciers covered 32% of the total land area

– Glaciers sculpt mountains and carve out valleys and canyons

– When retreating, glaciers leave behind evidence

– Inquiry Activity: Effects of Glacier Movement • Spread out your playdough on the lab bench – Landscape • Scrape your glacier, gravel end down, across your landscape – One direction, slow movement, pressure • What type of impressions did the glacier leave on the landscape? Was there any debris left behind? • When finished, set your glacier on the paper plate to melt

– Glaciers form on top of rocks and dirt but also pick up additional sediment as they move

• Moraines – Rocks and gravel that build up along the sides and end of the glacier as it advances – Deposits are left behind when glacier retreats

• Rock striations – Ice and debris stuck in the ice scratch the surface of other materials

• Erratic boulders – Large boulders left behind as glacier retreats

• Eskers – Long winding ridge of sand gravel – Formed in tunnels by streams that flow under glaciers – After ice melt away, stream deposits remain

• Drumlins – Small tear-drop shaped hills – Formed when glacier moves over a moraine – Tip of hill points in the direction that the glacier was moving

• Kettle lakes – Formed when glaciers scour out depressions in the land – Large chunks of ice are left behind and melt