Lecture 4 09 09 2014 We ve been talking about Plates Plate boundaries Directions Rates Hot spots A little about Earthquakes A little about Volcanoes Will be talking about tsunamis in part 2 of the course Ocean history Pangea to now and into the future There is no oceanic crust older than about 200 million years o b c ocean basically reforms itself the fact that we know the age of the ocean floor allows us to picture what the earth looked like prior to 200 millions years ago 09 09 2014 ocean into the future projection of plate tectonics what it may look like in the future new trench Western Atlantic Trench Central Indian Trench Pangea Proxima What we believe it will look like in the future wont happen for a VERY long time we will never know 09 09 2014 Sea level About 100 meters onto continental shelves Sea levels rises and sinks What causes sea level to change Sea level depends on ice on land o if you lock up more water on ice sheets that s lower sea level o sea ice does not affect sea level it is already floating think of it like ice in a cup when frozen and when melted it takes up same amount of space in cup ocean temperature o water expands when it warms up so as the ocean warms the sea level rises o most of sea level rising is because oceans are warming shape of ocean basins o think of shallow pan with water in it wont be too high of a level but if you put it in a skinny pot it will look higher level How do you get ice on land Transported through the atmosphere deposited as rain or snow How do you build an ice sheet You get snow every winter but if summers are not hot enough to melt all of that snow then you will start the next winter with some of that extra snow so over hundreds of years it builds up on land Sea level and global temperatures change together Cold periods have lots of ice on land low sea level Warm periods have less ice on land high sea level How do you measure sea level Usually with tide gauges o Record levels Sea level rise can have dramatic consequences for life on land 09 09 2014 Rivers Parts of a river Headwaters o Mountainous regions where things are pretty steep o Where rainfall or run off of snow collects o Flow fast and steep o Actual amount of water is not actually that much Flood Plain o Where the water comes out of the mountains and settles o It is added water due to rain o Where the river is wider and slows down o Sort of loopy o Can be described as Places that can be underwater when there is too much water for the river to carry Delta o Where the river meets the ocean o The river slows way down o River drops any sediment in it Headwaters Lots of big rocks rapids waterfalls Moves fast and jagged can cut through rocks as it goes Where river rafting is best Flood Plains Places where you are not in mountains Moves more smoothly Lots of agriculture around usually o When these areas get flooded they become very fertile Flood plain is underwater at least part of the time due to climate Delta Marked by sand and mud these are the sediments that come out of the rivers 09 09 2014 Most natural disasters are quick Earthquakes last seconds Tornadoes rarely touch down for a few mins Hurricanes come and go in matter of hours Floods disasters in slow motion Can last as long as the rain continues to fall as long as water continues to rise Some can drag on for weeks or months 09 09 2014 There are rivers on every continent Rain falls on land water flows downstream collects at low points o Different sizes shapes lengths volume transport Some of the major rivers of the world North America o Missouri o Mississippi o Ohio o Colorado o Columbia South America o Amazon largest river on earth by volume of water Africa o Nile longest river o Congo Southeast Asia o Ganges o Indus o Yellow o Yangtze Drainage Basins Places on continent that flow into similar oceans 09 09 2014 Pangea Breakup supercontinent 200mya go back over these parts did not take notes on them Tethys ocean Formation of Atlantic Formation of Himalaya mountains Sea level changes Storage on land ice and groundwater Thermal expansion Continents move Ocean basins change shape Sea level during the Ice Age lower Rivers Major world rivers location length and or discharge Parts headwaters flood plains delta Drainage basin Flooding sediment transport next time 09 09 2014 09 09 2014