A boundary is a real or imaginary line that separates two things. In geography, boundaries separate different regions of Earth. There are many different types of boundaries.

Physical Boundaries

Boundaries separate people and places. The most obvious type of boundary is a physical boundary. A physical boundary is a natural barrier between two areas. Rivers, mountain ranges, oceans, and deserts are examples. 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.

Rivers are common boundaries between nations, states, and smaller political areas, such as counties. The United States' Mississippi River is the defining boundary between many of the states it winds through, including 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. When these plates move around, they can cause large cracks in the earth, called fault lines. Volcanoes and earthquakes are more likely to happen along fault lines.

The fault line between the Pacific and North American plates makes the U.S. state of California more likely to have 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. 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, Germany's eastern border was moved farther west. The country itself was later divided into East Germany and West Germany.

In 1803, the United States bought a massive piece of land in a treaty with France. This land, called the Louisiana Purchase, expanded the size of the U.S. The western boundary of the U.S. moved from the Mississippi River to what is now Yellowstone National Park. The U.S. gained areas we now know as Missouri, North Dakota, South Dakota, Minnesota, New Mexico, Colorado, and many more.

An important type of political boundary in the United States is the boundary of a congressional district. This is an area that elects a representative to the U.S. House of Representatives. Its drawing depends on the findings of the U.S. Census, a population survey of the country taken every 10 years. If the population of a state grows or shrinks, that state may gain or lose a representative in the House. When this happens, congressional district lines are redrawn.

Other Boundaries

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

Language boundaries form between areas where people speak different languages. Often, these boundaries match political boundaries. For example, the most common language in France is French.

In India, more than 100 different languages are spoken. The Indian government recognizes 22 of these as official languages. People who speak these languages are generally split into different regions. Not being able to speak a neighboring region's language can cause tensions between people.

Economic boundaries divide people with different levels of wealth. Sometimes these boundaries happen along borders between countries. The border between the wealthier country of the United States and the less-wealthy country of Mexico is both an economic boundary and a political one.

Sometimes, economic boundaries fall within a single country, and even within a single city. For example, Manhantan's Upper East Side, in New York, New York, is a wealthy neighborhood. It has famous colleges and hospitals. The Bronx's Melrose is a poorer neighborhood just a few kilometers (miles) away from the Upper East Side. Its residents struggle to access the excellent education and healthcare available just a couple kilometers away.

Natural resources also play a part in economic boundaries. Some people settle in areas rich in resources, like underground oil or fertile soil. These people are more likely to become wealthy, while people who live in areas without many resources stay poor. People are also willing to pay more to live in areas with access to better resources. This might be beautiful views, excellent schools, hospitals, or access to shopping.

Social boundaries occur where differences between groups' ways of life lead to unequal access to resources and jobs. Some of these boundary issues include race, gender, religion, 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 forced to stay in different neighborhoods. Bahrain is a country in the Middle East. Many people from Southeast Asia have moved to Bahrain to find work. 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 native Bahrainis.

Social boundaries can also form along religious lines. The nation of Sudan has many distinct religious social boundaries. Northern Sudan has people mostly following Islam, while southwestern Sudan is mostly Christian. Sudan suffered more than 20 years of civil war, and the people of southern Sudan voted to leave Sudan as a separate nation, called South Sudan, in 2011.

Language, economic, and social boundaries are not as sharply defined as political and natural boundaries.

 

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

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.

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.)