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

Physical Boundaries

A boundary separates people and places.

A physical boundary is created by nature. Rivers, mountains, oceans, and deserts are examples of physical boundaries.

Sometimes, physical boundaries also form boundaries between countries or states. For example, mountains form the boundary between France and Spain.

Rivers are common boundaries. The Mississippi River divides several states. Louisiana and Mississippi have the Mississippi River as a boundary.

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

Sometimes, the plates spread apart from each other. This can cause continents to break apart. Millions of years ago, Africa and Europe were connected. Tectonic plates broke them apart.

When plates move around, they can cause large cracks in the ground. These are called fault lines. Volcanoes and earthquakes are more likely to happen along fault lines.

A fault line is near the U.S. state of California. This area is more likely to have earthquakes.

Political Boundaries

Political boundaries are lines drawn by governments. They divide up countries, states, counties, and cities. These areas are governed by different groups.

Sometimes, political boundaries follow physical boundaries. Most of the time you cannot see them. Most maps show political boundaries.

Political boundaries change over time. Wars, agreements, and trade force this change. After World War II, Germany was divided into East Germany and West Germany.

In 1803, the United States bought a huge land area from France. This event was called the Louisiana Purchase. The U.S. border moved farther west. It gained areas we now know as Missouri, Minnesota, North Dakota, South Dakota, and many more.

Other Boundaries

Other boundaries can be created by people. They are often harder to see. Still, they are very much felt.

Language boundaries form between areas where people speak different languages.

Often, these boundaries match political boundaries. For example, French is spoken in France. The main language in Spain is Spanish. Not being able to speak a neighboring region's language can cause tensions between people.

Economic boundaries involve wealth. They divide groups by how much wealth each has.

Sometimes these happen along borders. One example is the border between the United States and Mexico. The U.S. is much wealthier than Mexico.

Sometimes, economic boundaries happen within one city. For example, the Upper East Side is a wealthy neighborhood in the U.S. city of New York, New York. It has good colleges and hospitals. Melrose is a poorer neighborhood in New York. It is just a few kilometers (miles) away. Its residents struggle to get the excellent schooling and healthcare that exists nearby.

Natural resources also lead to economic boundaries. Some people settle in areas rich in natural resources. Areas with good soil for farming are examples. People there are more likely to become wealthy. Some people live in areas with fewer resources. They often stay poor.

Different groups often have different ways of life. This can lead to unequal treatment.

Until 2019, in Saudi Arabia all women must have a man watching over them. Women need permission to travel, seek healthcare, use money, or marry. This boundary discourages many women. They often cannot become leaders 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. They hope to find work there. Some Bahrain government leaders forced Southeast Asians to live in certain areas, away from others in the country.

Sudan is a country in Africa. It has many religious social boundaries. In northern Sudan, people 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. It became an independent nation in 2011. It's called South Sudan.