The most obvious type of boundary is a physical boundary. A physical boundary is a naturally occurring barrier between two areas. Rivers, mountain ranges, oceans, and deserts can all serve as physical boundaries. Many times, political boundaries between countries or states form along physical boundaries. For example, the boundary between France and Spain follows the peaks of the Pyrenees Mountains, while the Alps separate France from Italy. 

The Strait of Gibraltar is the boundary between southwestern Europe and northwestern Africa. This narrow waterway between the Atlantic Ocean and the Mediterranean Sea is an important political, economic, and social boundary between the continents. 

Rivers are common boundaries between nations, states, and smaller political units such as counties. The Rio Grande forms a large part of the boundary between Mexico and the United States. The Mississippi Riveris the defining boundary between many of the states it winds through, including Iowa and Illinois, Arkansas and Tennessee, and Louisiana and Mississippi.

Another type of physical boundary lies below Earth’s surface. Earth’s shell, or crust, is made of thick slabs of rock called tectonic plates. There are seven major tectonic plates and many smaller ones. These plates are constantly moving. 

Interaction between tectonic plates creates activity on their boundaries. Sometimes, the plates spread apart from each other, creating ocean trenches and, eventually, continents. This is called a divergent boundary. Sometimes one plate slides underneath the other, creating volcanoes and earthquakes. This is called a convergent plate boundary. Sometimes the plates grind past each other, creating earthquake fault lines. This is called a transform fault or transform boundary.  

The movement between the massive Pacific plate and the plates that border it creates all three types of boundaries. This tectonically active area is called the Ring of Fire. The divergent boundary between the Cocos and Nazca plates creates the Galapagos Ridge, off the coast of South America. The convergent boundary between the Pacific and Australian plates makes the island nation New Zealand a very active volcanic region. The transform fault between the Pacific and North American plates makes the U.S. state of California proneto earthquakes. 

Political Boundaries

Political boundaries are the dividing lines between countries, states, provinces, counties, and cities. These lines, more often called borders, are created by people to separate areas governed by different groups. Sometimes, political boundaries follow physical boundaries, but most of the time you can’t see them. Most maps show political boundaries. 

Political boundaries change over time through wars, treaties, and trade. After World War II, the mapof Europe was almost completely redrawn. Germany’s eastern border was moved farther west, and the country itself was later divided into East Germany and West Germany. 

In 1803, the United States bought 2,147,000 square kilometers (828,800 square miles) of land in a treaty with France, called the Louisiana Purchase. This land expanded the size of the U.S. to include the areas that are now Arkansas, Missouri, Iowa, Oklahoma, Kansas, Nebraska, and parts of Minnesota, North Dakota, South Dakota, New Mexico, Montana, Wyoming, Colorado, and Louisiana. The western boundary of the U.S. moved from the Mississippi River to what is now Yellowstone National Park.

An important type of political boundary in the United States is the boundary of a congressional district. A congressional district is an area that elects a representative to the U.S. House of Representatives. After the U.S. Census, which is taken every 10 years, the population of a state may grow or shrink enough to gain or lose a representative in the House. When this happens, congressional district lines are redrawn in a complicated and controversialprocess called redistricting. The boundaries between congressional districts may unite or divide economic, social, or ethnically distinct neighborhoods.

Other Boundaries

Political boundaries are just one type of artificial, or man-made, boundary. Other boundaries created by people include linguistic, economic, and social boundaries.

Linguistic boundaries form between areas where people speak different languages. Often, these boundaries match political boundaries. For example, the predominantlanguage in France is French, and the predominant language in Germany is German. 

In India, 122 different languages are spoken, each by more than 10,000 people. The Indian government recognizes 22 of these as “official languages.” People who speak these languages are generally split into different geographic regions. Inability to speak a neighboring region’s language can cause difficulties and tensions between people and businesses. 

Economic boundaries divide people with different incomes or levels of wealth. Sometimes these boundaries fall on national borders. The border between the developed country of the United States and the underdeveloped country of Mexico is an economic boundary as well as a political one.

Sometimes, economic boundaries fall within a single country, and even within a single city. For example, Manhattan's Upper West Side, in New York, New York, is a wealthy neighborhood with internationally recognized universities and hospitals. The Bronx's Melrose neighborhood, also in New York, is a low-incomeneighborhood whose residents struggle to access the excellent education and healthcare available only a few kilometers away. 

Natural resources also play a role in economic boundaries. People who settle in areas rich in resources—whether it is underground oil or fertile soil—are more likely to become wealthy, while people who live in areas without many resources tend to stay poor. People are also willing to pay more to live in areas with access to natural or economic resources: beautiful views, excellent schools, hospitals, and convenient access to shopping facilities.

Social boundaries occur where social differences lead to unequal access to resources and opportunities. Some of these boundary issues include racegenderreligion, and physical abilities. In some places, women may not have access to certain jobs or be allowed to travel in certain areas. In Saudi Arabia, for instance, all women must have a male guardian. This guardian’s approval is required for women to travel, seek healthcare, manage personal finances, marry, or divorce. This social boundary discourages many women from seeking leadership positions in business or government.

People of different races may be voluntarily or forcibly segregated into different neighborhoods. In Bahrain, political leaders have outlined plans to force the country’s Southeast Asian population to move to parts of the country where they will not live in communities with ethnic Bahrainis. Because most of Bahrain’s Southeast Asian population is made up of immigrant laborers, this social boundary is also an economic one.

Social boundaries can also form along religious lines. The nation of Sudan has many distinct religious social boundaries. Northern Sudan is mostly Muslim, southwestern Sudan is mostly Christian, and southeastern Sudan has more followers of animism than the other two regions. Sudan suffered more than 20 years of civil war, and the southern part of the country voted to secede from Sudan as a separate nation, called South Sudan, in 2011. 

Linguistic, economic, and social boundaries are not as sharply defined as political and natural boundaries. These types of boundaries are often transition zones.

 

Boundary
Like many boundaries, the thin line between the Earth's atmosphere and outer space is constantly changing.

Boundary Survey
A boundary survey establishes the exact property lines of a parcel of land. Boundary surveys are carried out by surveyors and engineers using historical records, field observations, and careful measurement.

Personal Boundary
Personal boundaries are the physical and emotional boundaries a person establishes around himself or herself. Different people have different boundaries: Some people reject most physical contact, such as a handshake, upon greeting. Other people embrace when they meet.

Maritime Boundary
A maritime boundary divides the ocean into areas controlled by different governments or no governments at all. The United Nations Convention on the Law of the Sea establishes a maritime boundary no more than 200 nautical miles (370 kilometers/230 miles) from a nation's coastline.

animism
Noun

religious belief that there are spirits throughout nature.

Noun

natural or artificial line separating two pieces of land.

Noun

line separating geographical areas.

Christian
Noun

people and culture focused on the teachings of Jesus and his followers.

city
Noun

large settlement with a high population density.

Noun

one of the seven main land masses on Earth.

controversial
Noun

questionable or leading to argument.

convergent plate boundary
Noun

area where two or more tectonic plates bump into each other. Also called a collision zone.

Noun

political unit smaller than a state or province, but typically larger than a city, town, or other municipality.

Noun

rocky outermost layer of Earth or other planet.

Noun

area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.

developed country
Noun

a nation that has high levels of economic activity, health care, and education.

divergent boundary
Noun

area where two or more tectonic plates are moving away from each other. Also called an extensional boundary.

earthquake
Noun

the sudden shaking of Earth's crust caused by the release of energy along fault lines or from volcanic activity.

economic
Adjective

having to do with money.

fault
Noun

a crack in the Earth's crust where there has been movement.

fertile
Adjective

able to produce crops or sustain agriculture.

finances
Noun

budget, or money available for a specific project or goal.

gender
Noun

physical, cultural, and social aspects of sexual identity.

Noun

study of places and the relationships between people and their environments.

govern
Verb

to make public-policy decisions for a group or individuals.

House of Representatives
Noun

federal branch of Congress in the United States, with state representatives elected every two years.

immigrant
Noun

person who moves to a new country or region.

income
Noun

wages, salary, or amount of money earned.

linguistic
Adjective

having to do with language or speech.

Louisiana Purchase
Noun

(1803) land bought by the United States from France, extending from the Mississippi River to the Rocky Mountains, and Canada to the Gulf of Mexico.

Noun

symbolic representation of selected characteristics of a place, usually drawn on a flat surface.

mountain range
Noun

series or chain of mountains that are close together.

Muslim
Adjective

having to do with Islam, the religion based on the words and philosophy of the prophet Mohammed.

Noun

political unit made of people who share a common territory.

natural resource
Noun

a material that humans take from the natural environment to survive, to satisfy their needs, or to trade with others.

Noun

an area within a larger city or town where people live and interact with one another.

Noun

large body of salt water that covers most of the Earth.

Noun

a long, deep depression in the ocean floor.

official language
Noun

language adopted by the government of a nation or other political unit.

oil
Noun

fossil fuel formed from the remains of marine plants and animals. Also known as petroleum or crude oil.

peak
Noun

the very top.

predominant
Adjective

leading or most influential.

prone
Adjective

vulnerable or tending to act in a certain way.

race
Noun

arbitrary grouping of people based on genetics and physical characteristics.

religion
Noun

a system of spiritual or supernatural belief.

representative
Noun

someone or something who acts in place of a group of people.

Noun

horseshoe-shaped string of volcanoes and earthquake sites around edges of the Pacific Ocean.

Noun

large stream of flowing fresh water.

soil
Noun

top layer of the Earth's surface where plants can grow.

state
Noun

political unit in a nation, such as the United States, Mexico, or Australia.

tectonic plate
Noun

massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate.

trade
Noun

buying, selling, or exchanging of goods and services.

transform boundary
Noun

site of tectonic plates sliding next to each other in opposite directions. Also called a transform fault.

transform fault
Noun

boundary between two tectonic plates, where the plates are moving horizontally or vertically in opposite directions, not against or away from each other. Also called a conservative plate boundary.

transition zone
Noun

area between two natural or artificial regions.

treaty
Noun

official agreement between groups of people.

underdeveloped country
Noun

country that has fallen behind on goals of industrialization, infrastructure, and income.

Noun

count of everyone in the U.S., conducted every 10 years.

Noun

an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.

war
Noun

large-scale armed conflict.

wealth
Noun

amount of money or other valuable materials.

World War II
Noun

(1939-1945) armed conflict between the Allies (represented by the United States, the United Kingdom, and the Soviet Union) and the Axis (represented by Germany, Italy, and Japan.)