Geography I: Key Geographical Skills and Physical Geography

This is Unit Ten of Social Sciences and History, part one of two: geography from its five questions to the plate boundaries. Unit nine closed on the postwar economic order. This unit opens the geography band, twenty percent of the exam, and this part carries one idea: geography asks where and why there, and every tool in it answers one of five questions, location, distribution, association, interaction, or change. The maps, the grid, the layers of a GIS, the regions and the diffusions are all ways of answering those questions, and the physical earth is read the same way, as a pattern that records a process. By the end of the part you will read a mountain range and a rift valley as answers to the question, what happened here. By the end you will be able to name which question an item asks. To say what a projection trades and what scale means. To locate a place two ways. To classify a region and a diffusion. And to read a plate boundary from its landforms.

Four entries on geography's questions: two branches, the spatial perspective, five kinds of question, and the maps in our heads.

What geography is.

SSH 0901 Writing About the Earth: Geography's Two Branches

Geography means writing about the Earth: the spatial study of physical and cultural environments. Physical geography covers the planet's physical systems; human geography, culture, spatial relationships, and human-environment interaction. GIS and remote sensing are where the jobs have grown. Geography is broader than area studies, the anchor insists.

The spatial perspective.

SSH 0902 Where and Why: The Spatial Perspective

Science is the systematic examination of nature's structure and functioning and a growing body of knowledge, with the Greeks' natural philosophy as its ancestor; geography applies it spatially, asking where things are and why there. Maps are how spatial organisms relate to a world they must first locate. Finlayson's spatial perspective names the same habit.

Five kinds of question.

SSH 0903 Five Kinds of Geographic Question

The exam may ask what kind of question a geographer is asking, and Dastrup supplies five, after Nyerges: location, where something is; distribution, how a phenomenon is spread across space; association, what is found together and why; interaction, how places affect one another through movement and exchange; and change, how a pattern alters over time. The geographic inquiry process moves from a question through data to a conclusion. Where is the aquifer: location. How are the wildfires spread across the state: distribution. Why do vineyards and limestone soils occur together: association. How does the port's trade shape the inland towns: interaction. How has the coastline moved since nineteen hundred: change. Ask whether the question wants a point, a pattern, a pairing, a flow, or a trend. The trap is calling every map question a location question; distribution and association also use maps. The second trap is interaction against association: association asks what sits together, interaction asks what moves between. These five are the idea this lecture runs on.

Mental maps.

SSH 0904 Mental Maps and the Inquiry Process

Mental or cognitive maps are the maps of our environment stored in our brains, used daily to travel, plan, and situate news. They are rough sketches reflecting how much geographic knowledge and spatial awareness we hold: a commuter's map, detailed near home and blank elsewhere. They reveal what we know of where we live.

Seven entries on maps and tools: projection's trade, scale's two meanings, the graticule, the two special lines, site and situation, GIS, and remote sensing.

Projection.

SSH 0905 Projection: The Sphere Onto the Page

A projection transfers locations from the Earth's curved surface to a flat map, and distortion is unavoidable, as flattening an orange peel shows: area, shape, distance or direction suffer. On the Mercator projection Greenland appears larger than South America though it is much smaller, and the anchor names Mercator alone. Every projection trades one accuracy for another.

Scale.

SSH 0906 Scale, Two Meanings

Scale is the ratio of length or distance on the map to length or distance on the ground, one inch to a mile against one to a hundred. It can also mean a phenomenon's spatial extent, local to global. Large scale shows a small area in detail; small scale, a large area coarsely. Extent is the human geographers' usual meaning.

The grid.

SSH 0907 Parallels and Meridians

The graticule, latitude and longitude, gives every absolute location an address in degrees. Parallels are circles parallel to the equator, numbered by latitude from zero at the equator to ninety at the poles, with the Tropics at twenty-three and a half degrees and the polar circles at sixty-six and a half. Meridians are half circles joining the poles, numbered by longitude.

The two special lines.

SSH 0908 Prime Meridian and Date Line

The Prime Meridian is zero degrees longitude and passes through Greenwich, England; longitude counts east and west from it. The International Date Line roughly follows one hundred eighty degrees, and roughly, the anchor says, because the line is not straight. The equator is zero degrees latitude and divides the Northern and Southern Hemispheres, with eastern and western hemispheres beside.

Site and situation.

SSH 0909 Site Against Situation

Site describes a location by its physical characteristics: topography, vegetation, climate. Situation describes it by the area surrounding the place, its relative location. The two answer different questions: what is this place like, and what is it near, a river-bend site against a situation between two markets. Situation is sometimes called relative location; site is absolute in flavor.

GIS.

SSH 0910 GIS: Layers of Data

A geographic information system combines computer hardware and software to store, analyze and display geographic data with computer mapping in a system of data layers. Roads on one layer, soils on another, population on a third, overlaid to answer a spatial question: where does a floodplain overlap dense housing. The layers are the point. One map is not a GIS.

Remote sensing.

SSH 0911 Remote Sensing

Remote sensing is the acquisition of data about the Earth's surface from aerial platforms: satellites, airplanes, or drones, a satellite image of a burn scar for instance. It feeds the layers a GIS analyzes, and with GIS it is the field where geography's employment has grown most, Dastrup says. Sensing gathers; the system analyzes.

Four entries on location, region and diffusion: locating a place two ways, three kinds of region, classifying a diffusion, and determinism against possibilism.

Locating a place two ways.

SSH 0912 Absolute or Relative? Locating a Place Two Ways

The exam gives a description of a place and asks whether it locates by absolute or relative means, and the anchors define both. Absolute location is a position on the graticule: degrees of latitude north or south of the equator and longitude east or west of the Prime Meridian, an address that never changes and depends on nothing nearby. Relative location, the anchor's situation, describes a place by what surrounds it: its distance and direction from other places, its position on routes, its neighbors. Site, the physical character of the place, is a third description, neither coordinate nor neighbor. Forty degrees north, seventy-four west: absolute. At the mouth of the Hudson, a day's sail from Boston: relative. On a deep natural harbor with a rocky shore: site. Downstream of the capital on the main rail line: relative. Ask whether the description would still hold if every other place vanished; only the absolute one would. The trap is treating a street address as absolute; it is relative to a city's grid, which is why the anchor reserves absolute for coordinates. The second trap is site against situation: site is what the ground is, situation is what the ground is near.

Regions.

SSH 0913 Formal, Functional, Perceptual Regions

A region shares a characteristic that binds it into a whole. A formal region is defined by homogeneity in one or more characteristics. A functional region is defined by a central node to which other places connect, a city and its commuters. Finlayson adds the vernacular region, the South as felt. Formal by sameness; functional by connection; perceptual by belief.

Classifying a diffusion.

SSH 0914 Expansion or Relocation: Classifying a Diffusion

Diffusion is the spread of ideas, objects, inventions and practices from place to place, and the exam asks which type a case shows. Expansion diffusion spreads outward from a core area that holds the idea, and it takes two forms: contagious, by person-to-person contact like a disease, and hierarchical, down a hierarchy, from large cities to smaller ones or from leaders to followers. Relocation diffusion occurs when people migrate and carry their ideas and objects with them, so the idea moves with the movers and the core may empty. The test is whether the core keeps the idea while it spreads, and whether spread follows contact or rank. A rumor passing through a crowded market is contagious expansion. A fashion adopted first in the capital, then in provincial cities, then in towns, is hierarchical expansion. A cuisine appearing in a new country with its immigrants is relocation. A technology taken up by headquarters before branch offices is hierarchical. Ask first whether the carriers stayed or moved, then whether the path was proximity or status. The trap is calling any migration-borne spread expansion; if the carriers left, it is relocation. The second trap is hierarchical against contagious: distance governs one, rank the other, and both are expansion.

Determinism and possibilism.

SSH 0915 Determinism Against Possibilism

Environmental determinism holds that the natural environment shapes and creates cultures, that environment essentially dictates culture. Possibilism holds that people can adapt to environmental conditions and choose among many alternatives despite the limits the environment poses: a desert people who irrigate, choosing among possibilities rather than obeying the sand. The exam pairs them.

Seven entries on the physical earth: hazards and the Ring of Fire, Earth's layers, the rock cycle, Wegener, three boundaries, two margins, and reading a boundary from its landforms.

Hazards and their seasons.

SSH 0916 Hazards Have Seasons; The Ring of Fire

Plate tectonics explains why nearly ninety percent of earthquakes and volcanoes occur along the Pacific's outer edges, the Ring of Fire. Hazards have seasons: tornadoes in spring and early fall, wildfires in late summer, hurricanes peaking in August and September, and America has more tornadoes than the rest of the world combined. Hazards are taught here as process, not safety lines.

Earth's layers.

SSH 0917 Crust, Mantle, Core

Earth is an oblate spheroid, flattened at the poles and bulging at the equator, known from seismic waves and meteorites. Chemically it has three layers: crust, mantle, core. The crust comes in two kinds: continental, low density and granite-like; oceanic, higher density and basalt-like, especially when cold and old. Chemical layers and physical layers are two different cuts.

The rock cycle.

SSH 0918 The Rock Cycle

The rock cycle begins with magma, molten rock below the surface, or lava, erupted above it; cooling crystallizes minerals into igneous rock, from ignis, fire. Weathering breaks rock into fragments and erosion removes them; the sediments, gravel to clay, become sedimentary rock. Heat and pressure make metamorphic rock. Minerals are the cycle's units.

Wegener.

SSH 0919 Wegener's Evidence and Its Missing Mechanism

Alfred Wegener, a German meteorologist, published in nineteen ten a hypothesis that the continents had moved: continental drift. His evidence: coastlines fitting like a jigsaw, South America's bulge in Africa's bight, and matching fossils across oceans, noted since eighteen fifty-eight. He lacked the mechanism, and plate tectonics later supplied it. The exam asks what Wegener had and what he lacked.

The three boundaries.

SSH 0920 Convergent, Divergent, Transform

Tectonic plates, made of oceanic and continental lithosphere, move partly by drag from the asthenosphere and by density. Their interactions at boundaries drive mountain building, earthquakes and volcanism. Where plates move toward each other the boundary is convergent; apart, divergent; past each other, transform. Toward, apart, alongside. The landforms each produces are read at the end of this part.

Margins.

SSH 0921 Active and Passive Margins

Where oceanic and continental plates meet and move relative to each other is an active margin, the Americas' western coasts. Where continental lithosphere passes into oceanic lithosphere without movement is a passive margin, their eastern coasts: earthquakes on one coast, quiet on the other. A plate may hold both kinds. Margin describes a coast; boundary describes plates.

Reading a boundary.

SSH 0922 Reading a Boundary From Its Landforms

The exam describes a landscape and asks which plate boundary made it, and Dastrup's three categories, joined to its chapter on structures, give the reading. Convergent boundaries, plates moving toward each other, produce compressional stress, thickening: mountain ranges, deep trenches where one plate descends, explosive volcanoes, and reverse faults where the hanging wall rises. Divergent boundaries, plates moving apart, produce tensional stress, stretching and thinning: mid-ocean ridges, rift valleys, new crust, and normal faults where the hanging wall drops. Transform boundaries, plates sliding past each other, produce shear stress: strike-slip faults with horizontal motion, frequent earthquakes, and little volcanism. Active margins host the first and third; passive margins, none. A trench offshore, volcanoes inland and thick crust: convergent. A long ridge with a central valley and fresh basalt: divergent. A straight fault along which the two sides have moved sideways for miles, with earthquakes and no volcanoes: transform. A mountain chain of folded rock with reverse faults: convergent, continent against continent. Ask which stress the rocks record: squeezed, stretched, or sheared. The trap is expecting volcanoes at every boundary; transform boundaries have few. The second trap is the fault names: reverse for compression, normal for tension, strike-slip for shear. The landform is the pattern; the stress is the process. That is the lecture's idea in stone.

Look at what you can now do. You can name which of five questions an item asks by whether it wants a point, a pattern, a pairing, a flow, or a trend. You can say every projection trades one accuracy for another, that scale is a ratio or an extent, and that the graticule gives every place an address in degrees. You can locate a place absolutely or relatively by asking whether the description would hold if all else vanished, and tell site from situation. You can classify a region by sameness, connection or belief, and a diffusion by whether the carriers stayed or moved and whether the path was proximity or rank. And you can read a plate boundary from the stress its landforms record, squeezed, stretched or sheared, which is where and why there, asked of the earth itself. Part two opens on faults and epicenters, then carries volcanoes, weathering, water, weather and climate to the anthropogenic signal.