Lesson 16: Coastal Dynamics Geological Oceanography

The Earth’s coasts There are two main ways to classify coasts: 1) based on location and 2) based on coastal formation Coasts are constantly changing as a result of natural processes Human activities also modify the coasts

Coasts can be classified based on geological location Active coasts are close to plate boundaries where plate collisions result in volcanoes and earthquakes Passive coasts are far away from plate boundaries and have little volcanic activity and earthquakes

Identify the active and passive coasts Plate boundaries are shown in bright yellow Is the Pacific coast active or passive? What about the Atlantic coast? Active! It is right near a plate boundary Passive! It is far from a plate boundary Photo: NOAA

Coasts can also be classified based on the way that they are formed Primary coasts Secondary coasts Definition Formed by processes not related to ocean activity (more land-driven) Formed by marine activity Formation processes Land erosion Plate tectonic activity Sedimentation Wave erosion Building by marine life

Two types of primary coasts Photo: USGS Deltas Wide continental shelf Accumulated sediment forms a triangular shape Volcanic coasts Volcanoes build up on the sea floor, eventually breaking the surface and forming island chains Nile River Delta Teacher’s Note: There are multiple types of primary and secondary coasts. Two examples of each were chosen to fit best within the lesson’s time frame, and your students should be aware that there are others. Photos: Nile River Delta http://eros.usgs.gov/imagegallery/; Accessed: November 2010 Hawaiian Islands http://coris.noaa.gov/portals/hawaii.html; Accessed: November 2010 Photo: NOAA Hawaiian Islands

Two types of secondary coasts Photo: NASA Marine-deposition coast Sea action causes sediment accumulation in one place forming mud flats, salt marshes, beaches and barrier islands Coasts built by organisms Organisms build structures like coral reefs and mangroves Barrier Island, Mexico Photos: Barrier Island Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center ISS016-E-22098 Great Barrier Reef http://photojournal.jpl.nasa.gov/target/Earth?subselect=refine%3Ayes&sort=ASC&start=4; Accessed: November 2010 Photo: NASA Great Barrier Reef, AUS

Coasts are dynamic, constantly changing What types of processes do you think might affect coasts? Natural processes like wind, waves, currents and erosion move sediments and change primary and secondary coasts Erosion refers to the breakdown and transport of sediment, sand, rock and other material by physical forces Wind and waves can move sand and other sediment and can wear away rocks near the shore

How do human activities shape the coasts? Human activities can impact coastal processes, as well In today’s activity, we will explore the effects of a manmade navigation channel on a delta in Louisiana