Shorelines Bob Leighty GLG 101 - Physical Geology

These notes and web links are your primary “lecture” content in this class. Additionally, various articles are assigned each week to supplement this “lecture” information. I believe you’ll have enough information to reference without having to purchase a costly textbook. These lecture notes are very similar to the ones I use in my traditional classes. You’ll find they are loaded with imagery and streamlined text that highlight the most essential terms and concepts. The notes provide a framework for learning and, by themselves, are not meant to be a comprehensive source of information. To take advantage of the global knowledge base known as the Internet, I have included numerous hyperlinks to external web sites (like the Wikipedia, USGS, NASA, etc.). Follow the links and scan them for relevant info. The information from linked web sites is meant to supplement and reinforce the lecture notes – you won’t be responsible for knowing everything contained in them. As a distance learning student, you need to explore and understand the content more independently than in a traditional class. As always, I will help guide you through this learning adventure. Remember, email Dr. Bob if you have any questions about today’s lecture (rleighty@mail.mc.maricopa.edu). Leave no questions behind! Explore and have fun!

Shorelines Why Do We Care? WWW Lots of people live at/near the shore

Shorelines Why Do We Care? Nature vs. people

Shorelines Why Do We Care? Nice scenery - recreation

Shorelines Why Do We Care? Did other planets have oceans too?

Shorelines All About Waves A wave (water, sound, light, etc.) is not a physical object – it is a moving pattern of up & down motion

All About Waves Wavelength (meters) - Distance between wave crests Shorelines All About Waves Wavelength (meters) - Distance between wave crests Amplitude (meters) – Height of crest from an undisturbed state Frequency (1/sec) – # of wave crests passing any point per sec wavelength () = velocity / frequency

All About Waves As ocean waves approach the shore ... Shorelines All About Waves As ocean waves approach the shore ... ... water depth decreases, wave speed decreases, wave height increases, & ...

Shorelines All About Waves ... and then the wave starts to break!

This 1946 breaking tsunami wave is over 6 meters high! Shorelines All About Waves This 1946 breaking tsunami wave is over 6 meters high!

… and then bend toward the shoreline Shorelines Nearshore Currents Waves slow as they reach shallow water … … and then bend toward the shoreline

Shorelines Nearshore Currents Longshore currents - Net current movement down the beach Longshore drift – Sediment movement parallel to shore

Nearshore Currents Rip current - Carries water back out to sea Shorelines Rip current - Carries water back out to sea Surfer-dudes use them

Types of Shorelines Erosional Wave refraction erodes headlands Occur as land is uplifted or sea level drops Common at active continental margins (West Coast, USA; glaciated areas also)

Types of Shorelines Erosional Headlands eroded into sea cliffs, stacks, arches, wave-cut platforms, etc.

Types of Shorelines Depositional Sediment deposited by currents Occur as land sinks or sea level rises Common at passive continental margins (East Coast,USA)

Types of Shorelines Depositional Spits, hooks, baymouth bars, barrier islands Drowned rivers (estuaries)

Shorelines Shoreline Problems Developing beach areas can easily change beach dynamics Erosion problems are typically hard & expensive to fix

Shorelines Shoreline Problems Ballast (boulders) & sea walls - stop erosion, but no beach left Beach nourishment – sand pumped onshore, but expensive

Shorelines Shoreline Problems Jetties - trap sediment on one side, but cause erosion on the other

Shorelines Shoreline Problems Groins - trap sediment on one side, but cause erosion on the other

Shorelines Shoreline Problems Breakwaters – Shield beach from waves, but sediment accumulates behind Tombolos – Natural breakwaters

Shoreline Problems Bottom-line solution: move somewhere else! Shorelines Bottom-line solution: move somewhere else! In 2000, the Cape Hatteras lighthouse was from its original location at the edge of the ocean to safer ground 2870 feet inland.

WWW Links in this Lecture Shorelines > Beach - http://en.wikipedia.org/wiki/Beach > Wave - http://en.wikipedia.org/wiki/Wave > Wavelength - http://en.wikipedia.org/wiki/Wavelength > Frequency - http://en.wikipedia.org/wiki/Frequency > Ocean wave - http://en.wikipedia.org/wiki/Water_wave > Longshore drift - http://en.wikipedia.org/wiki/Longshore_drift > Rip current - http://en.wikipedia.org/wiki/Rip_current > Headlands - http://en.wikipedia.org/wiki/Headlands_and_bays > Sea stack - http://en.wikipedia.org/wiki/Stack_%28geology%29 > Arch - http://en.wikipedia.org/wiki/Natural_arch > Wave-cut platform - http://en.wikipedia.org/wiki/Wave-cut_platform > Spit - http://en.wikipedia.org/wiki/Spit_%28landform%29 > Baymouth bar - http://en.wikipedia.org/wiki/Baymouth_bar > Barrier island - http://en.wikipedia.org/wiki/Shoal > Estuary - http://en.wikipedia.org/wiki/Estuary > Beach nourishment - http://en.wikipedia.org/wiki/Beach_nourishment > Jetty – http://en.wikipedia.org/wiki/Jetty > Breakwater - http://en.wikipedia.org/wiki/Breakwater_%28structure%29 > Tombolo - http://en.wikipedia.org/wiki/Tombolo