ANALYSIS of
Know the "rules" of interpreting rock sections... older than, younger than... meaning... MATERIALS
Monument Valley exercise -- Rules to remember ... Super____; Cross-______; Tilting means _____.
Roll out the nine chapters of Utah's geologic past... for Salt Lake County... note... not to scale for time... Chapter 1 is over half of the timeline!
Now... shift to LANDFORMS that we see and the processes that have made them look the way they do.
MANTRA!! TECTONICS RULE... All landforms are the product of TECTONICS and Erosion/Deposition. .
BIG CONCEPTS of PHYSICAL GEOGRAPHY
REGIONS – one of 5 "Great Themes" of geography
REGIONS are relatively extensive areas that are more similar within their boundaries than beyond their boundaries. They are drawn by people who have opinions as well as knowledge on the subject. Regions are based on spatial variation of a SPECIFIC CHARACTERISTIC. For example, regions based on surface water = drainage basins LINK.
Physiographic provinces are (by definition) regions
based on LANDFORMS.
Repeat: TECTONICS RULE!! Landforms result from processes of TECTONICS and
EROSION/DEPOSITION … usually both sets of processes working in tandem.
TECTONICS is the Great Cause of Earth’s Uplifts (and
down-warps, down-drops… but not down-cuts)
ISOSTASY (floats like an iceberg) is included in
TECTONICS as is volcanism and other igneous activity.
So… today… we’ll discuss
TECTONICS
Global --
Regional --
Local –
Global -- DANCE of the PLATES. –
Regional – Interactive UNAVCO http://www.unavco.org/software/visualization/GPS-Velocity-Viewer/GPS-Velocity-Viewer.html
Screen shots from the website: Basin and Range LINK; WesternUS LINK; WesternHemisphere LINK.
--
Local – evidence of GPS; evidence of seismic activity
Re-enact the spreading of the Basin and Range -- teams of two.
LINK;
evidence of faults
LANDFORMS… how divide into regions? topography? LINK; same info, DEM? Sterner; physiographic provinces by landform; RiddAtwood; Ridd landforms, GA provinces.
and regions relate to human geography... cities... hospitals
ANALYSIS OF UTAH LANDFORMS by PHYSIOGRAPHIC PROVINCE
I. Basin and Range physiographic province
Tectonic setting – extensional and active… thin crust being ever stretched out and broken
BLOCKS
Landforms:
Big expressions: basins and ranges
Local expressions:
·
closed basins (and closed basin lakes, sediment depo-centers,
shorelines, etc)
·
fault related (scarp, chopped off mountain fronts with
chopped off whatever-was-in-the-way, triangular facets, greatest snow on Earth,
etc)
·
ranges (run north south because extension pulls east
west, low at both ends and high in the middle, usually one side steeper than
the other because range front faults are usually not equally active)
· Low is depositional = basins with basin fill
Basin and Range characteristics LINK
Tectonic setting – very stable, thick crust, isostatic
equilibrium… (does not play well with others)
Landforms:
Big expressions: major massive
mountainous terrain with broad “parks”
Local expressions:
·
Mountains of many shapes and sizes (depending on
erosion/deposition histories)
·
Drainages of many shapes and sizes
·
Lots of glacial activity (more farther north)
·
Both erosion and deposition. Both bedrock and
sediments.
·
Low and erosional = valleys, “open” not closed,
marshes, fresh water lakes
III. Colorado Plateau physiographic province
Tectonic setting – very stable…. And rising
isostatically (not fast and pretty evenly) because so much material is being
eroded, the “base of the iceberg” rises … may be confusing… land surface
gradually lowering, but rock units rising. Careful… the upwarps and downwarps
pre-date “today’s” conditions.
Landforms:
Big expressions: big bold brassy red
extensive, nearly-flat lying, relatively undisturbed, layered sedimentary
bedrock exposed as plateaus, mesas, etc.
Local expressions:
·
Mesas, etc
·
Low and erosional = canyons
BIG QUESTIONS:
How did the high country get high? – By province…
How did the low country get low? – By province…
Is the high country getting higher?
Is the low country getting lower?
Tectonics sets the stage…
Erosion / deposition act on it
What is essential for having a lake?
Great Salt Lake 1960s;
Great Salt Lake 1980s;
Concept of a hydrograph.
Concept of a closed basin... review... what has made the basins of the Basin and Range? Mantra!!
What if climate changed from hot and dry of the past 10,000 years to wetter and colder?
Present thoughts about why? and how often? Ice Ages have happened "recently"
Mantra!!
Global Glacial versus Global Interglacial times LINK NOAA conveyor belt LINK
Great Salt Lake and Lake Bonneville Map 73 LINK; Just Great Salt Lake LINK; Just Lake Bonneville LINK ; Shorelines - LINK
Calendar exercise
Identify the province; point to (even if you don’t
know their names) several landforms in the photo.
