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


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Geography, Human Geography, Physical Geography, Social Studies, World History

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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

People and places are often separated by boundaries.

An obvious type of boundary is a physical boundary. It is a natural barrier between two areas. Rivers, mountains, 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 Mississippi River is the defining boundary between Arkansas and Tennessee, for example.

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. These create 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 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, agreements and trade. After World War II, for example, Germany was divided into East Germany and West Germany.

In 1803, the United States bought a vast land area from France called the Louisiana Purchase. It greatly expanded the size of the United States. 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, 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. This population survey of the country is 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

Not all boundaries are created by nature or governments. They may be less clear and harder to define.

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, hundreds of different languages are spoken. 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 groups by how much wealth each has. Sometimes these boundaries happen along borders between countries. One example is the border between the wealthier country of the United States and the less-wealthy country of Mexico.

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

Natural resources also play a role in economic boundaries. Some people settle in areas rich in resources, like fertile soil for farming. People here are more likely to become wealthy. People who live in areas without many resources often stay poor.

People are also willing to pay more to live in areas with better resources. These might include beautiful views, excellent schools, hospitals, or access to shopping.

Different groups often have different ways of life. This can sometimes cause unequal access to resources and jobs. Some of these boundary issues include race, gender, religion, and physical abilities. Until 2019, in Saudi Arabia each woman had to have a male guardian. Only he can allow her to travel, seek healthcare, manage money, or marry. 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 Middle Eastern country. Many people from Southeast Asian countries, like the Philippines and Indonesia, have moved to Bahrain to find work. Bahrain government leaders forced Southeast Asians to move to different parts of the country. There, they do not live among native Bahrainis.

Social boundaries can also form along religious lines. The nation of Sudan has many separate religious social boundaries. Northern Sudan has people who mostly follow the religion Islam. Southwestern Sudan has mostly people following Christianity. These groups fought for more than 20 years. The people of southern Sudan voted to leave Sudan as a separate nation, called South Sudan, in 2011.

Fast Fact

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.

Fast Fact

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.

Fast Fact

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.

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Hilary Costa
Erin Sprout
Santani Teng
Melissa McDaniel
Jeff Hunt
Diane Boudreau
Tara Ramroop
Kim Rutledge
Hilary Hall
Mary Crooks, National Geographic Society
Tim Gunther
Jeannie Evers, Emdash Editing, Emdash Editing
Kara West
Educator Reviewer
Nancy Wynne
National Geographic Society
Last Updated

October 19, 2023

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