The Archean (ar-KEE-uhn) Period started about 4 billion years ago and lasted until about 2.5 billion years ago. That’s a looooooooot of zeroes! It was so long ago, that there isn’t much left to find from that time period. But we do know that life probably started during the Archean, and we’ve found a few fossils of bacteria that may be from that time!
Fancy Science Words
The period of time between 4 billion to 2.5 billion years ago when life may have begun on earth
Gases like carbon dioxide and methane that trap heat in the atmosphere and warm the planet
A very tough crystal that forms as magma or lava cools
Rock formed by sand and other small particles as they settle beneath the water
The process of water or wind wearing away rocks or soil over time
What Did the Earth Look Like?
Since there isn’t much left over from the Archean, it’s hard to say exactly what the earth looked like then. The atmosphere was probably thick with greenhouse gases like methane and carbon dioxide. There were probably continents then, but they would have been smaller than today. We do know that there were oceans of water because 4-billion-year-old zircon crystals have been found in sedimentary rocks.
How does that show us that the earth had water? Well, zircon crystals need extreme heat and pressure to form. They probably formed after giant meteorites hit the earth and turned the land into oceans of lava. Water erodes, or wears away, rocks and creates sand. When sand settles together underwater, it can form a sedimentary rock. So, for zircon crystals to get into sedimentary rock, they had to be eroded away by water.
Did you know that about 37% of methane in the atmosphere comes from cows? They should really cover their mouths when they burp!
What Was the Climate Like?
The sun was much younger during the Archean than it is now. That means that it wouldn’t have been as hot, and there would have been less light. Because the sun was so much weaker, the earth should have frozen solid during that time, but it didn’t! We aren’t totally sure why, but one theory is that all of the greenhouse gases in the atmosphere kept the planet warm. Actually, the earth was much hotter than it is today. The temperature was probably somewhere between 130-175° F (55-80° C)!
Fancy Science Words
Living creatures whose bodies are made of just one cell
Very tough single-celled organisms. Maybe the first things to ever live
Bacteria that don’t need oxygen to live
The process some living things use to make food from sunlight, carbon dioxide, and water
The process some living things use to make food from rocks and minerals
The time period from about 2.5 billion to 541 million years ago
What Lived Then?
There wasn’t much oxygen, and it was really hot, so only single-celled organisms could live during the Archean. Things like archaea (ar-KEE-uh) and anaerobic (an-uh-ROH-bic) bacteria. Archaea are kind of like bacteria. Some can make food by using photosynthesis or chemosynthesis. Archaea are really tough and can survive in harsh environments. Anaerobic bacteria don’t need oxygen to survive, which is why they would have been able to live during the Archean Period.
There are millions of different types of bacteria on earth. Some can make you sick, and some can make you healthy! They help you digest food, and they turn dead leaves into soil. Bacteria are everywhere!
That’s it for the Archean Period. Next time, we will talk about the Proterozoic (proh-ter-uh-ZOH-ic) Period. Life on earth is about to get more interesting!
Hello Reader, Writers, Teachers, and Children! Our earth is somewhere around 4.5 billion years old. And living things have existed on it for maybe 3.5 billion years. But humans have only been around for some thousands of years. Think of all that we’ve missed!
Dinosaurs, mega sharks, giant sloths, huge ferns, and really, really weird critters! New fossils are discovered every day. With each new discovery, we learn a little more about our past. In this article series, we will talk about the following periods and the plants and animals that lived during those times:
The first two sections, Archean and Proterozoic, cover portions of time known as eons. The other sections are periods that fall under the Phanerozoic Eon, which covers the time from 541 million years ago to today.
These articles will be written at about a Grade 5 reading level. I’ll do my best to make them fun and interesting to read at any age!
By the way, did you know that Tyrannosaurus Rex lived during the Cretaceous Period? I guess Cretaceous Park just doesn’t have that ring to it.
The Horses of Saint Mark, AKA The Triumphal Quadriga, are a set of 4 life-size bronze horse sculptures. These nearly 2000-year-old masterpieces have made an incredible journey!
Quick Fix Facts
Horses of St. Mark
Possibly cir. 100-200 CE
13 ft (3.96 m)
Their story begins in Constantinople where the horses were displayed as part of a quadriga at the hippodrome. Though it is not known when the horses first came to Constantinople, they were still on display there in 1204 when the city was sacked by Venetian forces during the Fourth Crusade.
The doge of Venice, Enrico Dandolo, is said to have chosen the horses personally to be taken to Venice as a victory prize. In order to transport the horses, their heads had to be removed. Collars were added to cover the damage, and the horses soon adorned the façade of Saint Mark’s Basilica in Venice.
Quick Fix Terms
A four-horse carriage used for chariot racing
A stadium used for horse and chariot racing
Chief magistrate of Venice or Genoa
The horses remained their until 1797 when Napoleon Bonaparte conquered the city and took them as a prize of his own. They were whisked away to Paris where they would crown a new monument, the Arc de Triomphe. After Napoleon’s defeat at Waterloo, the horses were returned to the façade of Saint Mark’s in 1815.
Where the magnificent horses will journey next is anyone’s guess, but for now, they can been seen resting just inside Saint Mark’s Basilica.
Helium is the second element on the periodic table, and the second lightest element in the universe. It has two protons, two electrons, and two neutrons.
Helium gets its name from the Greek word “helios”, which means “sun”, because it was first discovered surrounding the sun!
Type of Matter
Helium is a gas at room temperature, and it has no color or smell. There isn’t much helium on Earth because it’s so light that it floats off into space. Jupiter’s atmosphere has a lot of helium. In fact, it actually rains helium on Jupiter!
How was Helium Discovered?
Pierre Janssen first discovered helium in 1868. While watching a total solar eclipse in India, he noticed a yellow glow around the sun. When heat or electricity runs through an element, it will glow a certain color. The element glowing yellow around the sun was helium!
In 1889, William Hillebrand put a mineral called uraninite in acid. It made a gas as it dissolved. That gas was helium. He didn’t know that though!
Finally, in 1895, Sir William Ramsay did a similar experiment. He wasn’t looking for helium, but he found it! This was the first time that helium was discovered on earth.
Fancy Science Words
Total Solar Eclipse
When the moon passes between the earth and the sun and completely covers the sun
A mineral made up mostly of uranium and oxygen with some helium, lead, and other elements
A machine that smashes atoms and particles together at high speed so they can be studied
What is Helium Used for?
Helium is usually collected from natural gas. It is used to make party balloons, weather balloons, and blimps float! Particle accelerators, like the Large Hadron Collider in Switzerland, get really hot, so they use liquid helium to keep them cool. Helium is also used in car airbags to make them inflate quickly.
Did you know that Helium is a noble gas? Noble gases don’t react with other elements, so they don’t combine with them. Helium atoms don’t make bonds with other atoms, but they aren’t lonely. About a quarter of the atoms in the universe are Helium!
In the next article, we will learn about Lithium. Don’t forget to charge your batteries!