Beaches, dunes, bluffs, terraces

Beaches are the lands right along the shore of a water body (viewgraphs 2-3)
	-- can be made up of boulders, cobbles, pebbles, gravel, often with shells
	-- can also very commonly be made of sand
	-- the size mix of the clasts on the beach reflects wave energy:
		-- high energy environments remove smaller clasts, leavng sand+
		-- low energy environments deposit finer materials
	-- source of beach materials
		-- continental shelf materials offshore brought up and in during
			quieter weather, hauled back out in storms
		-- materials weakened and then dropped through wave action on cliffs
		-- river transported materials deposited offshore
	-- materials constantly in motion (viewgraphs 4 and 5)
		-- wave swash and backwash
		-- longshore currents
		-- eroded from high energy promontories; deposited in low energy embayments
		-- can be moved by winds, not just water, and form dunes and blowouts
	-- sand is most commonly dominated by quartz (Mohs 7) and feldspars (6-6.5):
		-- these are very hard minerals and, thus, resist the mechanical
			breakdown better than softer minerals
		-- they also tend to be less reactive, so they resist chemical
			breakdown better than other minerals
Beaches and associated dunes are constantly in motion
	-- this creates very challenging environments for plants 
		-- constant movement:  wind and water can reposition sand and soil
			exposing plants' roots or burying the whole plant
		-- wind can not only reposition sand and soil but it dries plants
		-- extreme temperature swings 
		-- sandy texture means soil dries out fast
		-- water at depth may be saline, which is very challenging for plants
	-- plant responses to these challenges:
		-- plants often low, prostrate, sprawling, with shallow roots
		-- silvery hairs and the microshading of leaf surfaces that provides
		-- water resistant burs for water transport and grabbing onto soil 
		-- salt segregation/succulence or salt excretion/salt glands
		-- often sticky (holding onto sand for cooling?)
	-- a lot of invasives -- iceplant (Carpobrotus edulis or Hottentot
		fig from South Africa -- yellow flowers; C. chilensis or sea fig from 
			South America -- magenta flowers)		 
Bluffs and terraces are hills and cliffs facing the sea (viewgraphs 6 and 7)
	--  geological processes raising them are ongoing and make for unstable 
		cliffs, windy environments
		-- Pleistocene ice meant lower sea levels --> cliffs
		-- seismicity raises blocks --> cliffs and marine terraces
	-- a lot more shrubs and subshrubs up here, often specialized 
		species or subspecies related to the California sage scrub found
		higher up (prostrate Isocoma menziesii; sea-cliff
		buckwheat or Eriogonum parvifolim; coastal Dudley or Dudleya caespitosa; 
		saltbush or Atriplex lentiformis)
	-- these shade into and share genera with California sage scrub
	-- lots of invasives here, too (Atriplex semibaccata; all
		sorts of iceplants such as annual Mesembryanthemum crystallinum and 
		perennial Malephora crocea)
Some images at end of viewgraphs (#8):
	--  sand verbena (Abronia spp.) draping over sand
	--  silver dune lupines (Lupinus chamissonis)
	--  California sagebrush (Artemisia californica), buckwheats, Dudleyas on bluffs)
	--  Abronia close-up





last revised: 09/13/21