Earth has an ice age.
Big sheets of ice cover the land. Sometimes the ice grows very large. Other times the ice melts away. This happens over a long time. It changes how our world looks. Can you imagine a world of ice?
Earth has an ice age.
Big sheets of ice cover the land. These sheets grow and shrink. Sometimes the ice is very large. Other times the ice melts away.
When it is cold, the ice grows. This makes the sea levels go down. When it is warm, the ice melts. This makes the sea levels go up.
Today, we live in a warm time. The ice is mostly at the poles.
Large ice sheets still stay in Antarctica and Greenland. Our world is still in an ice age.
Earth is in an ice age. This is called the Quaternary glaciation. It began 2.58 million years ago. It is still happening today.
During this time, the climate changes. It goes through glacial periods. These are cold times when ice sheets grow. They cover much of Europe, North America, and Siberia. Then, the world enters interglacial periods. These are warmer times when the ice shrinks. We are in a warm interglacial period now.
Many things cause these changes. One cause is the way Earth moves. These are called Milankovitch cycles. Earth's orbit changes shape. The tilt of Earth also shifts. Earth even wobbles as it spins. These shifts change how much heat the seasons get. This helps ice build up.
Other things matter too. Gas in the air, like carbon dioxide, helps control heat. When gas levels are low, the world cools. The movement of continents also helps. Moving land changes how ocean water flows. This can move heat around the planet. These many parts work together to shape our world.
The Quaternary glaciation is a long period of time for our Earth. It began about 2.58 million years ago. It is still happening right now. Geologists call this an ice age. This is because large amounts of ice stay on the land. We are currently in a warm part called an interglacial period.
During the cold glacial periods, huge ice sheets grow very large. These sheets once covered much of Europe, North America, and Siberia. Only the ice in Antarctica and Greenland stays today.
This ice age works through a cycle of warming and cooling. During glacial periods, ice sheets expand across the land. These sheets can change the shape of the Earth. They erode the ground and move dirt around. They also create millions of lakes. The ice can even change how rivers flow. When the world warms up, we enter an interglacial period. During these times, the big ice sheets start to shrink.
Scientists have worked hard to understand these cycles. People in the 18th and 19th centuries first began to learn about this. Later, many geologists went into the field to study the land. They mapped many different shapes left by the ice. They looked at things called drumlins and moraines. These are marks left on the ground by moving ice. These maps helped them see how the ice moved and melted.
Many things cause these big changes in our climate. One reason is the way Earth moves in space. These are called Milankovitch cycles. Earth's orbit changes its shape every 100,000 years. The tilt of Earth's axis also changes. This tilt affects how hot or cold our seasons are. Earth even wobbles as it spins on its axis. These movements change how much heat the Earth gets.
Other things help control the temperature of our planet. Gases in the air, like carbon dioxide, play a big role. When these gas levels are low, the Earth tends to cool down. The movement of continents also matters a lot. As land moves, it changes how ocean currents flow. For example, the Drake Passage opened 33.9 million years ago. This changed how water moved around Antarctica. These changes helped create the huge ice sheets we see today.
The Quaternary glaciation is a massive, ongoing period of Earth's history. It began approximately 2.58 million years ago (Ma). Geologists define an ice age by the presence of large land-based ice. Because the Antarctic ice sheet has existed continuously, the Quaternary is considered an ice age. We are currently living in an interglacial period called the Holocene. This is a warmer interval between the colder glacial periods.
This period works through a cycle of expanding and contracting ice. During glacial periods, massive ice sheets cover huge areas. These sheets once reached across much of Europe, North America, and Siberia. When the climate warms, we enter an interglacial period. During these times, the continental glaciers retreat and melt. Today, glaciers occupy only about 10% of Earth's land surface. They are mostly found in Greenland, Antarctica, and some mountain regions.
These cycles change the physical world in profound ways. As ice sheets move, they cause continental erosion of the land. They also deposit vast amounts of material in new places. The movement of ice can modify entire river systems. It also creates millions of lakes, including pluvial lakes far from the ice. The heavy weight of the ice can even cause isostatic adjustment. This is a process where the Earth's crust sinks under the weight.
Scientists have spent centuries uncovering the history of these cycles. During the 18th and 19th centuries, researchers first began to understand this process. Later, hundreds of geologists performed extensive fieldwork. They mapped specific glacial features to see where ice once flowed. They looked for drumlins, eskers, and moraines. They also studied striations, which are scratches in the rock. These features helped them trace the direction of ancient ice flow.
One major cause of these cycles involves Earth's movement in space. These are known as Milankovitch cycles. They are caused by changes in Earth's orbital properties. First, orbital eccentricity changes the shape of Earth's orbit every 100,000 years. Second, the axial tilt varies between 22° and 24.5° every 41,000 years. This tilt changes the contrast between summer and winter temperatures. Third, precession is a wobble in Earth's rotation that lasts 26,000 years. These cycles change how much seasonal melting occurs.
Atmospheric composition also drives these temperature changes. Carbon dioxide is a greenhouse gas that helps trap heat. Geological evidence shows that carbon dioxide levels have dropped by over 90% since the Mesozoic Era. Lower levels of carbon dioxide can lead to long-term cooling. This cooling helps continental ice sheets form. During the Quaternary, high carbon dioxide levels correspond to warm interglacials. Low levels correspond to cold glacials. Some scientists believe carbon dioxide acts as a feedback to these changes.
Finally, the movement of continents and ocean currents plays a vital role. As tectonic plates move, they change how heat travels through the oceans. For example, the Drake Passage opened 33.9 million years ago. This separated Antarctica from South America. It allowed the Antarctic Circumpolar Current to flow freely. This current isolated Antarctica from warm water and helped ice sheets grow. Later, the Isthmus of Panama formed about 2.6 million years ago. This change in land also altered how the oceans circulated heat.
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