Explain how physical processes form and distribute resources, and weigh the costs and benefits of using renewable, nonrenewable and flow resources

Learning goal: Explain how physical processes influence the formation and distribution of renewable, nonrenewable and flow resources, and evaluate the costs and benefits of using each type in terms of availability, sustainability, environmental impact and expense.

Three kinds of resource. A natural resource is any part of the environment that people use. Geographers group resources by how they renew. A nonrenewable resource forms so slowly — over millions of years — that the amount people use is effectively gone: coal, oil, natural gas, metal ores. A renewable resource can regenerate within a human time frame if it is not used faster than it regrows: forests, fish stocks, groundwater in many aquifers. Soil is a borderline case: it forms so slowly (often centuries or more for a single centimeter) that eroded soil is generally treated as nonrenewable on human time scales, even though good management can keep its fertility. A renewable resource can be depleted; overfishing and over-pumping are ways of turning a renewable resource into a shrinking one. A flow resource is available only as it occurs and must be used then or lost: sunlight, wind, the flow of a river, tides. Flow resources cannot be depleted by use — using today's wind does not reduce tomorrow's — but they vary by place, season and hour, and storing their energy requires batteries, reservoirs or other technology.

Physical processes and formation. Where resources are found is not random. It follows from physical processes operating over time.
- Tectonic activity plays a role in the formation and location of fossil fuels. Coal, oil and natural gas form from organic matter buried in sedimentary basins — low areas of the crust that sink and fill with sediment. Tectonic forces create many such basins, for example where the crust flexes downward beside a rising mountain belt. Burial raises temperature and pressure, which, over millions of years, turns plant material into coal and marine organic matter into oil and gas. Folding and faulting then create structures, such as arched rock layers capped by impermeable shale, that trap oil and gas. So fossil fuels are concentrated in particular basins and generally scarce in regions of ancient crystalline rock (oil formed in nearby sedimentary rock can occasionally migrate into fractured crystalline rock). Eastern Ohio's coal seams, for example, lie in the Appalachian Basin and formed from swamp vegetation roughly 300 million years ago.
- Erosion plays a role in the formation of sedimentary rocks. Weathering and erosion break rock into sand, silt and clay; rivers, wind and ice carry these particles and deposit them in layers; compaction and cementation turn them into sandstone, siltstone and shale. Sedimentary rocks matter as resources because they host fossil fuels, hold groundwater in porous layers, and supply building stone, sand and gravel.
- Rainfall patterns affect regional drainage patterns. Where rain is plentiful and spread through the year, dense networks of permanent streams usually develop and carry water toward the sea. Rainfall is one influence among several: rock type, soil permeability, groundwater and slope also shape how many streams form and whether they flow all year, and some rivers, such as the Nile, flow through deserts because they are fed by rain far upstream. In arid regions many streams are ephemeral, flowing only after storms, or intermittent, flowing only in wet seasons, although groundwater or rain far upstream can keep some rivers flowing all year; and some basins have no outlet to the ocean at all, so water evaporates and leaves salts. Drainage patterns decide where surface water, hydroelectric potential and fertile alluvial soils are found, which is why river flow, a flow resource, is distributed as it is. In Ohio, a drainage divide separates rivers that flow north to Lake Erie from those that flow south to the Ohio River and on to the Mississippi.
- Climate, water and soil govern renewable resources. Renewable resources form through ongoing physical and biological processes, so their distribution follows present-day climate rather than ancient rock. Forests grow where precipitation, temperature and soils support trees: dense tropical rainforest near the equator, where it is warm and wet all year; broad belts of coniferous forest across high-latitude Canada and Russia; and few trees in deserts, which are too dry, or tundra, which is too cold. Groundwater is replenished when rain or snowmelt soaks into the ground (infiltration) and seeps down into an aquifer, a layer of porous, permeable rock or sediment such as sandstone or gravel — often the sedimentary rocks described above. Recharge is fastest where precipitation is plentiful and the ground is permeable, and slowest in deserts, where some aquifers hold water that soaked in thousands of years ago and is replaced far more slowly than it can be pumped. Sunlight and wind, the flow resources, are distributed by latitude, cloud cover and the circulation of the atmosphere.

Distribution creates geography. Because processes are uneven, so are resources: a country may have abundant sunshine and little oil, or rich ore deposits and little farmland. Uneven distribution explains much of world trade and some political conflict, and it means that "resource-rich" always needs the question rich in what, where, and at what cost of extraction?

Costs and benefits. The standard lists four criteria for judging resource use.
- Availability: Is the resource present, accessible and reliable? Coal is dense, storable and available on demand; solar power is abundant in sunny regions but unavailable at night.
- Sustainability: Can use continue indefinitely? Flow resources and well-managed renewables can; nonrenewables cannot, because the stock declines with every unit used.
- Environmental impact: What happens to land, water, air and climate? Burning fossil fuels releases carbon dioxide and air pollutants; mining disturbs land; large dams flood valleys; wind turbines and solar farms occupy land and require mined materials to build.
- Expense: What does it cost to extract, build, transport and maintain? Costs include up-front construction, fuel, and costs borne by others, such as health effects of pollution, that do not appear in the price.
No resource wins on every criterion. The misconception to reject is that renewable or flow resources have no costs, or that nonrenewable resources have no benefits.

A worked model. A hypothetical town must choose a new electricity source and scores three options from 1 (poor) to 3 (good) on the four criteria. Coal: availability 3, sustainability 1, environmental impact 1, expense 2 — total 7. Wind: availability 1 (it varies), sustainability 3, environmental impact 2, expense 2 — total 8. River hydro at an existing weir: availability 2 (seasonal flow), sustainability 3, environmental impact 2, expense 2 — total 9. On equal weights hydro ranks first. If the town weights availability double because its hospital needs constant power, coal scores 10, wind 9 and hydro 11, and hydro still ranks first — but wind and coal swap places. The scores are hypothetical judgments, not measured data; the method shows that the ranking depends on which criteria a community values.

Worked example 1 — classify resources: Iron ore: nonrenewable, formed over geological time. Groundwater in a slowly recharging desert aquifer: renewable in principle but effectively depleted if pumping exceeds recharge. Tidal energy: flow resource, available with the tides, usually twice a day, and usable only as it occurs unless stored.

Worked example 2 — explain a distribution: Why are oil fields concentrated in some regions? Organic-rich sediment accumulated in subsiding basins; burial under more sediment heated it into oil; tectonic folding formed traps under impermeable rock. Regions made mostly of ancient igneous and metamorphic rock lack organic-rich source rock, so they generally lack oil, though oil formed in neighboring sedimentary basins can occasionally collect in fractured crystalline rock.

Worked example 3 — weighted cost–benefit: Using the lesson's hypothetical scores, weighting environmental impact double gives coal 3+1+2+2 = 8, wind 1+3+4+2 = 10 and hydro 2+3+4+2 = 11. Changing the weight changes the margin between options, which is why a cost–benefit judgment must state its weights.

Resource profile (record task): For one country or region, list two renewable, two nonrenewable and two flow resources. For each, name the physical process that explains its presence (tectonics, erosion and deposition, rainfall and drainage, climate).

Independent performance: Write a 400-word evaluation of one real resource decision, such as developing a coal seam, a wind farm or a hydroelectric project. Success criteria: you classify the resource type; explain its formation or distribution using a physical process; assess it on all four criteria — availability, sustainability, environmental impact and expense — with evidence; state who receives benefits and who bears costs; and make a recommendation that names the criterion you weighted most and why.