AP Environmental Science

## Learning Outcomes

- Explain why natural energy resources are unevenly distributed across Earth
- Distinguish between **resource**, **reserve**, and **proved reserves**
- Identify how geology, climate, topography, and tectonic activity control energy availability
- Apply examples of where fossil fuels, solar, wind, hydroelectric, and geothermal resources are most abundant
- Explain how uneven distribution affects trade, energy security, and environmental impacts
- Use this topic in AP Environmental Science multiple-choice and free-response questions

## AP Environmental Science Syllabus

For the AP Environmental Science, you are expected to understand uneven natural energy distribution, with a focus on the following syllabus points:

- Know that natural energy resources are not distributed equally across Earth
- Explain that **fossil fuels** are concentrated by geologic history, especially in sedimentary basins
- Identify that **solar** potential depends on high insolation, **wind** on strong steady airflow, **hydroelectric power** on water flow and elevation change, and **geothermal energy** on tectonic activity
- Explain the difference between a **resource**, a **reserve**, and **proved reserves**
- Understand the role of an **exploratory well** in identifying oil and natural gas deposits
- Apply examples of regions rich in oil, coal, natural gas, solar, wind, hydroelectric, and geothermal potential
- Explain how uneven distribution shapes imports, exports, energy dependence, and environmental trade-offs

## Test Your Knowledge

_Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, look more closely at that area during your revision._

1. Why are fossil fuels found in some regions but not others?
2. What is the difference between a resource and a reserve?
3. Why is solar energy strong in some places but weak in others?
4. Name one region with high geothermal potential and explain why.
5. How can a country have energy resources but still import fuel?

## Introduction

Uneven natural energy distribution means that energy resources are not spread evenly around Earth. Some regions have large coal deposits, some have major oil and natural gas fields, and some have little fossil fuel but strong solar, wind, hydroelectric, or geothermal potential. This pattern matters because energy access affects economic growth, industrial development, trade, and political power.

For AP Environmental Science, the key idea is simple: each energy source depends on specific physical conditions. **Nonrenewable** resources such as coal, oil, natural gas, and uranium depend mostly on geologic history. **Renewable** resources also show uneven distribution, but their pattern depends more on present-day climate, topography, and tectonic setting.

> **Key Term: uneven distribution of natural energy resources**
> The pattern in which energy resources are not located equally across Earth because their formation or availability depends on geology, climate, topography, and tectonic activity.

### Resource, reserve, and proved reserves

Students often lose marks because they use these three terms as if they mean the same thing. They do not.

A **resource** is the total amount of a naturally occurring material that exists, or may exist, and could potentially be useful. This is the broadest category. It includes material that has not yet been discovered, or that exists but is currently too expensive or difficult to extract.

A **reserve** is narrower. It is the known part of a resource that can be extracted profitably under current economic conditions using current technology. This means reserves can change over time. If oil prices rise, some previously uneconomic deposits may become reserves. If prices fall, some reserves may no longer be worth extracting.

**Proved reserves** are narrower still. These are discovered reserves that geologic and engineering evidence shows are highly likely to be recoverable under current conditions.

> **Key Term: resource**
> The total amount of a naturally occurring energy source that exists or may exist and could potentially be used.
>
> **Key Term: reserve**
> The identified portion of a resource that can be extracted economically with current technology and current prices.
>
> **Key Term: proved reserves**
> The discovered part of a reserve that is considered recoverable with reasonable certainty under existing economic and operating conditions.

This distinction matters because natural distribution is not the same as usable supply. A country may have a large resource base but a smaller reserve if extraction is difficult, expensive, or poorly explored.

> **Test Tip:** If an AP question asks what can be extracted profitably now, choose **reserve**, not **resource**. If it asks about the most certain category, choose **proved reserves**.

Another important term is **exploratory well**. This is a test well drilled to determine whether oil or natural gas is present. It helps geologists gather information about underground formations and may increase reserve estimates if the results are promising.

> **Key Term: exploratory well**
> A test well drilled to determine whether oil or natural gas is present and to collect geologic information about a possible deposit.

### Why nonrenewable energy resources are unevenly distributed

Fossil fuels are unevenly distributed mainly because they formed only in certain places under specific conditions over geologic time. They do not appear wherever dead organisms once lived. Large, usable deposits formed where organic matter accumulated, was buried, and then exposed to pressure and heat for millions of years.

Oil and natural gas are especially associated with **sedimentary basins**. These are regions where layers of sediment built up over long periods, often in ancient seas. Marine organisms died, accumulated in sediments, and were buried. Over time, heat and pressure changed the organic matter into hydrocarbons. The oil and gas then migrated and became trapped in porous rock layers under impermeable cap rock.

> **Key Term: sedimentary basin**
> A region where thick layers of sediment accumulate and where fossil fuels often form and become trapped.

Coal formed differently. It came mostly from ancient swamp vegetation. Plant material built up in wet, oxygen-poor conditions, forming peat that was later buried and transformed into coal. Because ancient swamp conditions existed only in certain regions, coal seams are clustered rather than universal.

This is why some regions became major fossil fuel producers. The Middle East became rich in oil because of its geologic history involving ancient marine environments and large sedimentary basins. The United States has major coal deposits in places such as Appalachia and the Powder River Basin because ancient environments there favored large plant accumulation and burial. Russia, the United States, China, India, and Australia also have major coal resources because their geologic histories supported coal formation.

Natural gas is somewhat more widely distributed than coal or oil, but it is still not evenly spread. The key point is that geology controls where these fuels formed. Technology may improve access, but it does not change the original pattern of where the fuels occur.

Students also need to avoid a common mistake: saying fossil fuels are found where they are “used most.” Use and occurrence are different. China uses large amounts of coal, but its consumption does not explain where coal formed. Formation happened over geologic time, long before modern industry.

### Why renewable energy resources are also unevenly distributed

Many students assume renewable means “available everywhere.” That is wrong. Renewable resources are replenished on human timescales, but their **quality and usefulness still vary greatly by place**.

Solar potential depends mostly on **insolation**, the incoming solar radiation reaching a location. Regions with high insolation, low cloud cover, and wide open land have the greatest solar potential. Deserts and dry subtropical regions are especially strong locations for solar energy.

> **Key Term: insolation**
> Incoming solar radiation reaching a given area.

The southwestern United States is a strong solar region because it has many sunny days, low cloud cover, and broad open land. Other strong solar regions include North Africa, the Middle East, Australia, and the Atacama Desert in Chile. By contrast, cloudy high-latitude areas receive less reliable solar energy, especially in winter.

Wind energy depends on strong, steady air movement. The best locations are open plains, coastal areas, mountain gaps, and offshore regions. These areass reduce obstacles and often channel or strengthen winds. The U.S. Great Plains are a major example. Northern Europe also has major wind development, especially in and around the North Sea.

Hydroelectric power depends on two things working together: reliable flowing water and elevation change. A region needs enough precipitation or snowmelt to maintain river flow, and enough relief to give the moving water kinetic energy. Flat dry regions are poor hydroelectric locations even if they have long rivers with limited gradient. Mountainous wet regions are much more favorable.

> **Key Term: hydroelectric power**
> Electricity generated by moving water, usually where river flow and elevation change allow turbines to be turned.

That is why places such as China, Brazil, Canada, Norway, and other mountainous river systems have strong hydroelectric potential. The physical reason is not simply “they have rivers.” It is that they have large rivers, sustained water input, and significant elevation differences.

Geothermal energy depends on Earth’s internal heat being close enough to the surface to use. This is most common near plate boundaries, volcanic regions, rift zones, and hotspots. Iceland is a classic example because of its tectonic setting on the Mid-Atlantic Ridge. The western United States also has strong geothermal potential because of tectonic activity and heat flow.

> **Key Term: geothermal energy**
> Energy obtained from heat within Earth, especially where underground heat is close enough to the surface to be used.

So the causes differ by resource:

- **Fossil fuels and uranium:** mainly geology
- **Solar:** insolation and cloud cover
- **Wind:** air circulation and landform
- **Hydro:** precipitation, river flow, and topography
- **Geothermal:** tectonic activity
  > **Test Tip:** In FRQs, do not just name a place. Always add the physical reason. For example: “Iceland has high geothermal potential because it lies in a tectonically active region where heat is close to the surface.”

### Regional examples and why they matter

AP questions often use real-world examples, so it helps to match resources to regions and then explain the pattern.

Oil is abundant in major parts of the Middle East, Russia, the United States, Canada, and Venezuela. The reason is geologic history, especially large sedimentary basins and hydrocarbon traps.

Natural gas is abundant in Russia, the United States, Iran, and Qatar. Again, this reflects geologic formation and trapping, not modern demand.

Coal is important in the United States, Russia, China, India, and Australia because ancient plant-rich environments created large coal deposits there.

Solar is strongest in the southwestern U.S., North Africa, Australia, and other dry sunny regions because these areas have high insolation and limited cloud cover.

Wind is strongest in the Great Plains, coastal China, offshore northern Europe, and Patagonia because these areas have steady winds and open exposure.

Hydroelectric potential is major in China, Brazil, Canada, and Norway because of river systems with high flow and strong elevation gradients.

Geothermal potential is high in Iceland, Japan, Indonesia, the Philippines, New Zealand, and the western U.S. because these areas are tectonically active.

These examples matter because uneven distribution shapes development. Countries rich in fossil fuels may become exporters and gain economic and political influence. Countries poor in domestic fossil fuels may depend on imports, which creates energy-security concerns.

This also explains why a country might still import fuel despite domestic resources. A country may have coal but little oil. It may have oil resources but not enough refinery capacity. It may import cheaper fuel while saving domestic reserves. Or it may have strong renewable potential but still rely on imports while infrastructure is being built.

### Environmental and political consequences of uneven distribution

Uneven distribution has more than one consequence. First, it shapes trade. Fuel-rich countries can export energy; fuel-poor countries often import it. This creates transport networks such as pipelines, tankers, and transmission lines, each with environmental risks.

Second, it affects **energy security**. Countries with limited domestic supply may be vulnerable to price shocks, supply interruptions, or political conflict elsewhere. If a nation relies heavily on imported oil or natural gas, distant events can raise domestic energy costs.

Third, it shifts environmental burdens. Extraction does not happen evenly either. Coal mining, oil drilling, natural gas development, large dams, wind farms, solar arrays, and geothermal drilling all affect local environments. So resource-rich regions often carry a larger share of habitat disruption, pollution risk, and land-use change.

Fourth, it affects which energy transitions are easiest. A dry sunny region may move into solar faster than a cloudy one. A tectonically quiet region cannot simply choose geothermal at large scale. A mountainous wet region may have hydroelectric opportunities that flat dry regions do not.

This is why AP Environmental Science expects you to connect physical geography with human choices. Energy decisions are not made on a blank map. They are shaped by what nature has placed where.

## Key Point Checklist

_This article has covered the following key knowledge points:_

- Natural energy resources are unevenly distributed across Earth
- Fossil fuel distribution depends mainly on geologic history
- Oil and natural gas are concentrated in sedimentary basins
- Coal formed where ancient swamp vegetation accumulated and was buried
- Renewable resources are also unevenly distributed
- Solar potential is highest in regions with high insolation and low cloud cover
- Wind potential is greatest in plains, coasts, mountain gaps, and offshore areas
- Hydroelectric power depends on reliable water flow and elevation change
- Geothermal energy is strongest in tectonically active regions
- A resource is broader than a reserve, and proved reserves are the most certain subset
- Exploratory wells help identify oil and gas deposits and refine reserve estimates
- Uneven distribution affects trade, imports, exports, energy security, and environmental impacts

## Key Terms and Concepts

- uneven distribution of natural energy resources
- resource
- reserve
- proved reserves
- exploratory well
- sedimentary basin
- insolation
- hydroelectric power
- geothermal energy


Distribution of Natural Energy Resources - Uneven natural energy distribution