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OUTLINE OF THE LECTURE – February 22, 2010 Urban Environmental Geography GEOSPHERE – Earth’s processes… materials… features
Announcements Rob and Jonathan… don’t leave the session without seeing me about Wednesday’s topics. ASSIGNMENT POSTED: LINK TO LINK TO USGS map and an interactive VERSION Expectations (DRAFT... to encourage preparation) for the midterm LINK
By the end of this session, you should: Appreciate that the geosphere is the “foundation” …
Every subsystem of Earth systems influences a city’s setting. The geosphere largely determines how a city can grow,
To understand the geosphere, it helps to understand:
Approach: On one screen, I’ll show the PowerPoint slides of Christopherson that are posted on WebCT. On this screen I’ll supplement with lecture notes and tie to urban environmental geography.
First, I’ll digress for a review of what is meant by “scale.” See your workbook, Chapter One, Section on Remote Sensing, Questions 2 through 5. Also LINK to http://edc2.usgs.gov/pubslists/factsheets/fs01502.pdf The problem… how do I know what the real-world distance is based on a map? “What’s the proportion, meaning the ratio, of what is measured on the map to what it represents on the ground?” Ratio…. What’s-its on the map versus What’s its on the ground 1 inch on the map = 24,000 inches on the ground (1:24,000 scale). 1 foot on the map = 24,000 feet on the ground (1:24,000 scale) 1 cm on the map = 24,000 cm on the ground (1:24,000 scale) Think… what’s the logic for 1:24,000 scale? 1 inch = 2,000 ft. 1:63,000 is an inch on the map is a mile on the ground.
And here's a good site for CONTOURS http://cimss.ssec.wisc.edu/wxwise/contour/
Geog3330 – BIG SCIENCE CONCEPTS Big Science Concept #1 – Conservation of Energy. In an isolated system, the total amount of energy stays constant, meaning, energy is neither created nor destroyed, it transforms from one energy form to another.
Big Science Concept #2 – Properties of gasses (and many liquids and solids) are inter-related: mass, volume, density, temperature, and pressure.
Big Science Concept #3 – Earth has many cycles.
Big Science Concept #4 – To make a budget, balance the components.
Big Science Concept #5 – Effects of Earth systems processes are cumulative.
LECTURE Some geology basic concepts…. PROCESS, MATERIALS, FEATURES… change Deep time…. Lots and lots of time for change to happen… 4.5 billion years that Earth has had a crust, has had rocks, has recycled its rocks / crust.
GEOLOGIC TIME SCALE… urban environmental geographers do not need to know the geologist’s terminology for time. Relative geologic time has been worked out by mapping which rocks are on top of others (younger if on top); where rock units cross (older if cut by the other); by fossils that show who life forms have changed through time; by some minerals that change their ratio of chemical isotopes. Summary: we look at rock layers. How is this important to urban environmental geographers? Humans have affected Earth systems processes sufficiently to leave a rock record of activity. A new geologic epoch… the Anthropocene.
EARTH’S STRUCTURE and internal energy. . Earth has a layered structure (also a theme of the atmosphere and, to a lesser extent, the hydrosphere, and biosphere). Cities are built on: (a) Earth’s crust, (b) on land, (c) generally on continents. LINK to USGS basic information about Earth’s structure: http://pubs.usgs.gov/gip/dynamic/inside.html LINK to a favorite tectonics website - paleomaps - global http://www.scotese.com/Default.htm -- And this animated version from UCBerkeley http://www.ucmp.berkeley.edu/geology/anim1.html LINK to website on volcanoes... how they work http://www.geology.sdsu.edu/how_volcanoes_work/ Draw on whiteboard, structure of Earth. GEOG3330 - GEOSPHERE is the entire, solid Earth
Summarizing concept, Structure of Earth. We live on Earth’s surface, so, naturally it matters to us a lot. We generally think of Earth’s crust as thick and say things like: finding resources deep within Earth, or earthquakes deep within Earth. But, Earth’s crust is to the skin of an apple as Earth is to the size of an apple… not the skin of an orange.
ENERGY… BIG SCIENCE CONCEPT #1… Forces work on Earth’s crust from inside out and outside in. The result is change, inexorable and slow and “dynamic Earth.” Energy drives those forces.
ISOSTASY – floats like an iceberg. SKINNER ISOSTASY Does this matter for urban environmental geographers. In rare occasions, it matters a lot, such as places where areas rebound from having been depressed by ice or water, for example, from glacial ice of the Ice Age… northern Europe.
BIG SCIENCE CONCEPT #5… today’s concept… the past is the key to the present; the present is the key to the past; etc, including the future. Geology, the study of Earth, includes the study of Earth’s materials, Earth’s landscapes, and Earth’s processes.
BIG CONCEPT #3… Earth has many cycles. From the perspective of an urban environmental geographer, what matters most about Earth’s materials is the contrast of sediments (loose… meaning not firmly coherently continuously attached to Earth’s crust) versus bedrock (solid rock, firm, coherent, continuous part of Earth’s crust).
GEOLOGIC CYCLE … ROCK CYCLE. Does this matter to urban environmental geographers… yes… it matters to everyone, just as much as the water cycle. However, it takes about a week to learn it, solid. The series to understand:
The “rock cycle” is Earth’s process of recycling minerals via chemical and physical processes into different rock types. LINK to ROCK CYCLE… if you want to learn the rock cycle… I’ll coach you through it. Come to office hours.
THE ROCK CYCLE for urban environmental geographers. The ROCK CYCLE is how Earth recycles minerals, much as the water cycle is how Earth recycles water. Just as there are processes of the water cycle (e.g., evaporation, condensation, precipitation, surface runoff, etc) so there are processes of the rock cycle. ROCK CYCLE. In-course LINK SCHEMATIC. LINK to ESE Rock Cycle The ROCK CYCLE can be thought of as four products and four processes
SOILS are a special type of sediment. ROCK CYCLE... TRADITIONAL InCourse LINK
TECTONICS … the topic of the workbook… and of Wednesday’s session. A helpful LINK http://pubs.usgs.gov/gip/dynamic/dynamic.html
Plate tectonics is a now-well-established explanation of the movements of continents and oceans and the general architecture of Earth’s crust. (Note… most plates have both continental and oceanic crust.)That is not to say that the processes are totally understood. But it is to say that abundant, irrefutable evidence documents present and past movements of continents with respect to each other. A few definitions: Earth’s crust has two general types of crust: oceanic crust and continental crust. Note: when you think of crust, think of the bedrock, firm, rigid outer solid layer of Earth that floats on extremely hot, melted material of the next layers. Oceanic crust is more dense that continental crust, so it floats lower, and there water flows to it, and that explains why large ocean basins have oceans. Continental crust is less dense, and floats higher.
Take away concept for urban environmental geographers… tectonics (the processes that change the structure of Earth’s crust… that thin protective rocky crust) determine cities (a) scenery; (b) geologic resources; and (c) geologic hazards.
Scenery includes: landscapes, landforms, the lay of the land. The lay of the land can determine the layout of a city (how far it can extend, its linearity, how it connects to other places…)
Geologic resources: as continents drift, collide, divide, and, in the process change elevation, they distribute, concentrate, and disseminate resources. Resources determined by tectonics include swamplands that can be the source for coal; quiet shallow seas that can be a source for oil; intrusions of melted rock (magma) that can be the source for many minerals. Cities consume resources, many of which are determined by past tectonic environments.
Geologic hazards: tectonics largely determines a region’s elevation relative to sea level. Geologic hazards include hazards directly related to tectonics (earthquakes and volcanoes) and indirectly related to tectonics, those associated with steep terrain, and those associated with low terrain. Note: usually more than one process results in a geologic hazard.
Background… and clarification… TWO sets of inter-related processes. Forces acting on the outside of the crust, and those acting from the inside. Where does the energy come from that drives “dynamic” Earth?
TECTONICS: Earth’s geologic processes, specifically, tectonic processes can be studied at global, mega-regional (“plate”), regional, and local scales. Effects on cities can also be studied at those scales. Global tectonics: crustal movements, magnetic reversals, continental drift, dance of the plates, age of crust (migration of suites of geologic resources); earthquakes and volcanoes are related to plate boundaries; relative motion (hot spots)
REPEAT: The processes that affect Earth are generally (1) those driven by uneven distribution of heat WITHIN the Earth versus (2) those driven by uneven distribution of heat on the OUTSIDE of the geosphere. The ones WITHIN Earth drive TECTONICS, the processes by which portions of the crust move with respect to each other. The one OUTSIDE the geosphere are the ones that affect EROSION and DEPOSITION.
It’s pretty obvious why urban environmental geographers need to understand erosion and deposition (next few lectures). And… everyone should understand basics of tectonics because tectonics brings us hazards and the distribution of resources. CHRISTOPHERSON PowerPoints… evidence for tectonics, also called plate tectonics.
LINK to LINK to map that will be a reference for your homework assignment… tectonics and effects on your urban setting.
DANCE OF THE PLATES... GEOLOGY IS CUMULATIVE
MORE ON TECTONICS... lots more... These notes are supplementary. REFERENCES on TECTONICS. USGS website... careful, some of these links are old: http://pubs.usgs.gov/gip/dynamic/historical.html . For definition of plates, configurations from times of dinosaurs to present and more text and images for understanding plate motions: http://pubs.usgs.gov/gip/dynamic/understanding.html . Natural hazards and tectonics http://pubs.usgs.gov/gip/dynamic/tectonics.html . The pdf of the explanations of tectonics and more: This Dynamic Earth: http://pubs.usgs.gov/gip/dynamic/dynamic.html Plates: LINK to USGS map of plates today ; LINK to map of plates in motion MapOnlyDynamicPlanet ; LINK to types of plate boundaries USGS-PlateTectTypeBound ; For the western United States we can measure the stretching LINK to UNAVCO of and Stretch of western US Bargen; and that explains the stretching of the region from Salt Lake City to Reno LINK to Extension of Basin and Range; and Differential Motion that explains why earthquakes along the Wasatch Front are to be expected and their consequences are impressive LINK to XSectionOfEffects . (CHAPTER 9… commentary) Tectonics… global, mega-region, regional, and local Tectonics (including isostasy) determines elevation and relief – RELIEF is the DIFFERENCE in elevation between two places (steep, moderate, gentle) and can be quantified (from horizontal = zero). LANDSCAPES and LANDFORMS
MEGA-LANDFORMS – continents versus oceans… continental crust versus oceanic crust. Hypsometry … Topography Regions
GEOLOGY IS CUMULATIVE Tectonics drives the spreading of oceans, the drifting of continents Continental shields – old, stable, continental crust. How Earth recycles crust: crustal formation and destruction GEOLOGY IS CUMULATIVE… continents form over time; processes add to and subtract from them. Today… active tectonic accretion (added onto) … Alaska, Canada… change along OR – WA; another change along CA
GEOLOGY IS CUMULATIVE: Process, Materials, Features PROCESS Compressional tectonics = shortening Extensional = tension = lengthening Shear = at an angle FEATURES / LANDFORMS / LANDSCAPES Folds, faults, upwarps / downwarps; mountains / basins; MATERIALS caught up in collisions. Continental crust – less dense Oceanic Crust – more dense (think Geog3330 – Second Big Science Concept as well as First… and Fifth… gosh, and Third, and Fourth…. Meaning… keep thinking those big concepts) RESULT in structural regions (Christopherson slide) RESULT in earthquakes, volcanoes
URBAN ENVIRONMENTAL GEOGRAPHY … summary and reminders Past tectonics… largely responsible for setting of city. Think of it as a foundation. Past tectonics… largely responsible for geologic resources. Present tectonics… largely responsible for geologic hazards Present tectonics… also in part responsible for present geologic resources. Present tectonics… largely responsible for landscapes (scenery… quality of life as well as setting… tie to atmosphere, hydrosphere, biosphere… and anthrosphere).
More on TECTONICS… notes on Utah and tectonics… Salt Lake Valley. Note ... LINKS need to be relinked... not part of Feb 22 lecture. Earth’s crust consists of plates that move with respect to each other. The plates float on the weak, hot layer below them. As they move with respect to each other, they tend to collide (compression), pull apart (extension), or slide past each other (transform). DYNAMIC EARTH. DYNAMIC EARTH in cross-section to see relationships at the boundaries. PLATE BOUNDARIES DIFFERENTIAL MOTION Utah today is on the continent of North America. It also is on the North American plate. Note how the North American plate includes continental and oceanic crust. DETAIL for motions of the western US from BARGEN GPS; and BARGEN summary; UNAVCO Basin and Range extension LINK Intermountain seismic belt LINK Emergency management Utah’s faults LINK Utah’s historic seismicity LINK Wasatch fault recurrence LINK. Cross section of effects LINK; Wasatch fault shaking UGS Shaking PI76SLCo; Wave types LINK: Liquefaction LINK; Boundary of Utah’s Wasatch Line, or hingeline, or boundary between east and west STERNER RELIEF MAP Ridd multiple hazards BEGIN, eliminate END
Green Sheets. And… Rob and Jonathan… see me about Wednesday's plan. |
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{Students of Geog/Envst3330 -- for powerpoints of lectures, go to your UofU WebCT / Blackboard course files } {Problems viewing this site? Please contact genevieve.atwood@geog.utah.edu} {This page modified on January 2010- Modifications will continue through Spring semester 2010} |