Brrrr - The Ice Age!
Did you know that the last ice age ended approximately 11,000 years ago? And no, I am not talking about the movie. In science, an ice age is a long period of time during which Earth’s temperature is greatly reduced. Over the past 2.5 million years, the planet Earth has undergone approximately 20 ice ages! Geologists use ice ages to separate intervals of geologic time periods because the times of ice ages and mass extinctions generally line up. An example of this is a mass extinction from approximately 435 million years ago due to a drop in ocean level caused by an increase in glaciation. This increase in glaciation means that large territories were completely covered in ice, and is a way of referring to an ice age without specifically saying “ice age”. These expanses of ice are so crazy that glaciers today are actually just leftover chunks of ice from previous ice ages. Even the Antarctic ice sheet referenced in “Hydrology...Oceanography...Limnology...Glaciology! Oh, too many to count! - More on Glaciology'' is a dwarf compared to the structures of ice that are present during ice ages!
Despite the fact that we have had plenty of ice ages ranging in severity over the past billion years, there have been four major periods of glaciation within the past 800 million years. The first was in the late Proterozoic era at the end of the Precambrian time (between 800 and 600 million years ago). The next two were the late Ordovician ice age and the early Silurian ice age (between 460 to 430 million years ago), and the last one was during the Pennsylvanian subperiod of the Carboniferous and continued throughout the Permian period between 350 to 250 million years ago. We are actually even living in a smaller ice age now, and it will be marked in scientific history as one that began in the late Neogene period and continued into the Quaternary. Now, these are not just fancy names for time periods that I made up to confuse you. These complex names just help scientists understand which era is being referred to without having to know the exact year. You do not need to memorize the exact names of these eras right now unless you want to!
This raises questions about the human connection to the ice age. Because of this, some scientists believe that what we are living in is not an ice age but an interglacial period. An interglacial period is when glaciers cover a lot of Earth but oceans are not at peak levels. We know that ice ages have been happening for much longer than humans have been alive (Homo sapiens came into existence about two million years ago). However, since then, ice ages have still been present across the world, and different ice ages have played key features in human development. One ice age actually created a land bridge allowing Siberian peoples to migrate to the Americas. These are the Native Americans you have probably heard of in your history class!
A more recent ice age is the Little Ice Age which lasted from 1250 to 1850. This ice age is commonly covered in different classes in high school, especially World History. During the Little Ice Age, there was cooling and expansion of glaciers in the temperate latitudes. These latitudes are between the tropic and polar circles, and they have smaller differences in temperature from winter to summer. For a long time, this ice age devastated the European territories that it occurred in. Glaciers destroyed farmlands and buildings in the Alps, Norway, and Iceland, and parts of Greenland became impossible to live in. Across Europe, farming was a disaster, and many people died from famine.
Now, you might be wondering about how ice ages occur! By studying extraterrestrial (like sunspot activity and Earth’s orientation) and terrestrial factors (like the presence of meteorites), scientists have discovered some information about what causes ice ages. Typically, ice ages occur when summer temperatures in the northern hemisphere do not go above freezing for years because this does not allow snow and ice from the winter to melt. The ice and snow build up and compress forming glaciers and ice sheets that are key characteristics of ice ages.
As mentioned earlier, we are currently living in a period thought of as interglacial, so Earth could enter another ice age in several centuries. However, because of global warming, there have been large amounts of carbon dioxide and methane released into the air over the past two centuries due to industrialization. This may prevent us from entering another ice age, hurting our environment and the organisms that live in it. That is why we must do our best to help reduce global warming and practice sustainable habits!
Picture Credit: history.com
