SHORELINES
3/18/2011 draft for UVU -Intro Geology – March 30, 2011 –
(needs... handout... and check CBHunt ref; print out handout
Genevieve Atwood, Ph.D., guest lecturer
LINK to EncyBritannica-BreakingWaveOffKanagawa - Hokusai
THE OVERARCHING GOAL OF THIS CLASS SESSION IS:
Joy of Geology –
GEOSCIENCE the GLORIOUS ENTERTAINMENT
·
Recognizing shorelines of the past can be challenging
(and rewarding, sometimes).
· Recognizing components of shorelines (erosional versus depositional/constructional; delta surfaces versus shoreline evidence, etc) can give a sense of empowerment through understanding
Relevant... Japan, living on the shores of... .
THIS lecture assumes you already know about:
·
The Hydrologic Cycle (a.k.a. the water cycle). LINK to USGS
schematic
·
The Rock Cycle – includes how sediments are products
of sedimentation specifically… weathering, erosion, transport, and deposition LINK to ESE
rock cycle animation
By the end of this session, you should:
·
Understand what shorelines are … (narrow definition
and broad definition)
·
Begin to understand their variability… huge subject
·
Know where and how to look for shoreline evidence in
·
Perhaps be able to imagine how “your” shorelines were formed.
So What? Shorelines are great places to “see” Earth systems…
the interactions of geosphere, hydrosphere, atmosphere
(weather/climate), biosphere (living Earth), and anthrosphere (human
footprint).
Roadmap of today’s session: (a) some
terms; (b) some concepts of geology / Earth systems; (c) move from global to
local, including some of my work on Great Salt Lake and Lake Bonneville.
TERMS... .
Narrow definition: shoreline is the intersection of two
surfaces: (a) the surface of the water body, and (b) the surface of the land.
From Merriam-Webster on-line:
1: the line
where a body of water and the shore meet
2: the
strip of land along the shoreline
From Glossary of Geology, 5th ed., AGI iPhone ap
(American Geological Institute):
(a) The intersection of a specified plane of water
with the shore or beach; it migrates with changes of the tide or of the water
level. The term is frequently used in the sense of “high-water shoreline” or
the intersection of the plane of mean high water with the shore or beach, or
the landward limit of the intermittently exposed shore. … (Synonyms…)
(b) The general configuration or outline of the shore.
The terms “shoreline” and “coastline” are often used synonymously, but there is
a tendency to regard “coastline” as a limit fixed in position for a relatively
long time and “shoreline” as a limit constantly moving across the beach.
FIRST shorelines are associated with relatively large
water bodies.
To have a water body… necessary factors… must have a
place for water to be… and must have water.
Oceans - yes; Lakes - yes; … Ponds?
Global scene – Oceans (LINK to Norton-15.03 Global Coastlines;
and LINK to Norton-15.03abc added relief and tectonics)
For purposes of this talk… NOT going to explore how
the water body got there… and not how that-which-contains-the-water got there... there are several possible ways… tectonics, dams…
can’t go there today… but never forget tectonics.
BROADER DEFINITION
and how we talk about
"shorelines" here
Evidence… what might it be? (a) topographic
expression (shape, size, and slope); (b) materials; (c) all due to coastal
process (waves, currents, biota).
VIRTUAL TOUR of SHORELINES… Who has been to a great
shoreline… anywhere?
French
SHORELINES as landforms
LANDFORMS – are natural features on Earth’s surface with:
1. Characteristic
SHAPE
2. Characteristic
MATERIALS
3. Characteristic
PROCESSES that make them
And… all landforms have a history… they each tell a
story (just like every rock has a story)
DIAGRAMS… for an ocean but similar processes
Cross-section of a depositional (accreting): LINK to
Norton-15.15
Plan-view of shorezone… not
And 3-D of up-welling and down-welling along shore: LINK to
Norton-15.10ab
Field Guide to Shorelines... what to look for
LINK to HUNT sketch of Bonneville Shoreline LINK to Hamblin image of Point of the Mountain.
SHAPE: Virtually horizontal.
MATERIALS: Sediments
NOT like a RIVER... NOT like a deposit from a flash flood
PROCESSES: Erosion / deposition.
WHAT TO LOOK FOR:
Scenery - yes
Hazards – yes
·
Norton15.35a; Norton15.35b; --
·
USGS links among others:
http://coastal.er.usgs.gov/hurricanes/katrina/photo-comparisons/dauphin.html
Resources – yes – particularly if one
counts recreation (beaches) and ecosystem.
·
SFBay, example: http://sfbay.wr.usgs.gov/general_factsheets/coastal_resources.html
Science – yes
·
Why? Interfaces interest scientists… where change
happens…
·
East coast, continental shelf – LINK to Norton-15.05 NewEngland
Importance of shorelines… locally…
Great
Salt Lake and
Scenery – yes – particularly if you
appreciate the subtlety of the Basin and Range. LINK to Hamblin
Hazards – several… of GSL and of
paleo-shorelines of
·
For example, this landslide in
·
And... Sherwood Hills landslide studied by UVU undergrads
on topography steepened by Lake Bonneville shore processes LINK to UVU
undergrad poster by (Paul Gardner, Robert White, Jessica Oxford, Victoria Sailer, Adam Healey (Michael Bunds), 2008). The "bad-actor" bedrock is the direct cause of the ground failure, but the slope, oversteepened by Lake Bonneville coastal process probably contributes to instability.
Resources – important –
·
shoreline sand and gravel… for constructions LINK to
Hamblin Point of Mtn
·
benches for building sites, for example UofU, BYU,
WSU, parts of USU, on shoreline features of high levels of Lake Bonneville… and
UVU, too, on delta deposits. LINK back to UVU image from GoogleEarth shown before... look at all the construction.
Science –
·
Great Salt Lake –
Let’s go "collect" some shorelines …
1.
Modern
shoreline of a fresh water, shallow lake … What is special about Utah Lake?
2. Shoreline
evidence of the past… Can you see through the haze, into the distance and recognize shorelines of Lake Bonneville on the west side of Utah Lake?
3. Active deltas of Utah Lake … may be impossible to see.
4. Deltas of
past… trick question unless you recognize the obvious.
