The Beach, A River of Sand

1. The Beach, A River of Sand River of Sand Video

2. Berm: the nearly horizontal portion of the beach on the backshore formed by the deposition of sand

3. Where does sand come from?

5. From where do beaches come? • Sand, along with gravel, silt and clay are collectively known as sediment, and are produced by the mechanical and chemical breakdown of rocks. • Once disaggregated from the original source rock, this material is then eroded and transported by either wind, water, or ice, often ending up at the deposits of rivers or lakes, as sand dunes, or ultimately as sediment in the sea.

6. What about when there are no mountains? • In areas where there is no good source of sedimentary material from mountains or volcanoes, sand is often entirely composed of organic material i.e. shell fragments, coral, and the tests (skeletons) of small planktonic organisms. The sand is said to be “biogenic.”

7. Sand deposition

8. La Jolla, California Summer Beach Gentle waves pile sand on the beach

9. La Jolla, California Winter Beach Strong waves carry sand off the beach depositing it temporarily on off-shore sand bars

10. The shape of the beach is determined by how it formed… • Why is it better to surf in the winter?

11. it is all about sand movement

12. Sand created features

13. Longshore Drift consists of the transportation of sediment along a coast at an angle to the shoreline. It is dependent on 1. direction of the prevailing wind 2. swash (turbulent water that washes up on the beach) 3. backwash (offshore flow of water)

14. Natural Sand Deposition Features

15. What’s happening to Block Island?

17. a local tombolo

18. a local spit

19. Local barrier beaches on south shore

20. Some features are directly created by man

21. Rip Currents • Bands of fast moving water moving off shore • Look for a channel of choppy water with a noticeable color difference

22. DRAMATIC SEDIMENT FEATURES

23. Sea Arch

24. Sea Stack

25. Blow Hole blow hole Hawaii

26. Common constituents of sand: • Minerals: • Quartz : clear (doesn’t break down easily) • Feldspar : pinkish-tan • Mica: black and flaky • Olivine : olive • Hornblende : black/grey, dull • Garnet: reddish • Biogenic: • Coral • Shells • Foraminifera • Coralline algae • Rock: • Volcanic basalt (black islandic rock) • Granite

27. How oceanographers analyze sand… • Color  composition • Rounding  distance traveled or age • Size  strength of waves, wind, glacier • Pits  directly from volcano • Sorting  distance traveled, # of sources of material

28. … so scientists also know about the beach’s location by… • it’s steepness (from size) • what the parent material is (color) • distance the sand traveled to get there • the power of the beach’s waves (shape) • biogenic material…continental or island, tropical, temperate or polar • The influence of man (?)

29. Wentworth sediment size scale, and resultant beach shape, for example

30. What can you tell?

31. Beaches are important habitats Headlands – Point Reyes, California Look!

32. Elephant Seals

33. “Haul Out” to molt

34. beachmaster battle

35. FUN with sand!!

37. THE END