June 18, 2015
Silurian:
The Silurian (Pronounced Si-lure-ee-in) period was a time in Earth's history that started 443 Million Years Ago and ended 419 Million Years Ago. Following the second largest mass extinction (See the Ordivician article) in Earth's history, the Silurian replaced the extinct life forms. The Silurian saw the arrival of bony fish. Bony fish are fish that have bones instead of cartilage. At this time, animals had not fully gone onto land. Some insects like the millipede could go on land but t was mostly limited to millipedes and other insects. In the Silurian, the sea was filled with fish and other forms of life. Vascular plants (Plants on land) appeared for the first time. Interestingly, there were very little coral reefs during the Silurian. Next time, we will learn about the time period known as the Devonian period.
Silurian:
The Silurian (Pronounced Si-lure-ee-in) period was a time in Earth's history that started 443 Million Years Ago and ended 419 Million Years Ago. Following the second largest mass extinction (See the Ordivician article) in Earth's history, the Silurian replaced the extinct life forms. The Silurian saw the arrival of bony fish. Bony fish are fish that have bones instead of cartilage. At this time, animals had not fully gone onto land. Some insects like the millipede could go on land but t was mostly limited to millipedes and other insects. In the Silurian, the sea was filled with fish and other forms of life. Vascular plants (Plants on land) appeared for the first time. Interestingly, there were very little coral reefs during the Silurian. Next time, we will learn about the time period known as the Devonian period.
May 7, 2015
Ordovician:
The Ordovician (Pronounced Or-do-vish-in) period was a time in Earth that started 485 Million Years Ago and ended 443 Million Years Ago. The Ordovician continued what the Cambrian had started. Life continued to grow and diversify, or become different, as the years went on. Many forms of sea life came during this period of Earth's history. The term for life continuing to diversify in the Ordovician is known as the Great Ordovician Biodiversification Event. One of the more famous creatures to have evolved in this time period were the Trilobites. Although Trilobites had first appeared in the Cambrian period, they appeared in North America and Europe during the Ordovician. Other creatures evolved from during the Ordovician as well. Mollusks such as squid, and other cephalopods evolved during this time. At the end of the Ordovician period came the second largest mass-extinction in Earth's history. The cause of the mass-extinction is unknown however there are two existing theories. The first theory is that much volcanic activity led to the mass-extinction. The other theory is that a gamma ray burst (A gamma ray burst a blast of gamma rays from an exploding star. Go to the Waves and Rays section of Science All Around to learn more about gamma rays.) wiped out much of the life on Earth. Next time we will learn about the time period known as the Silurian period.
Ordovician:
The Ordovician (Pronounced Or-do-vish-in) period was a time in Earth that started 485 Million Years Ago and ended 443 Million Years Ago. The Ordovician continued what the Cambrian had started. Life continued to grow and diversify, or become different, as the years went on. Many forms of sea life came during this period of Earth's history. The term for life continuing to diversify in the Ordovician is known as the Great Ordovician Biodiversification Event. One of the more famous creatures to have evolved in this time period were the Trilobites. Although Trilobites had first appeared in the Cambrian period, they appeared in North America and Europe during the Ordovician. Other creatures evolved from during the Ordovician as well. Mollusks such as squid, and other cephalopods evolved during this time. At the end of the Ordovician period came the second largest mass-extinction in Earth's history. The cause of the mass-extinction is unknown however there are two existing theories. The first theory is that much volcanic activity led to the mass-extinction. The other theory is that a gamma ray burst (A gamma ray burst a blast of gamma rays from an exploding star. Go to the Waves and Rays section of Science All Around to learn more about gamma rays.) wiped out much of the life on Earth. Next time we will learn about the time period known as the Silurian period.
May 2, 2015
Cambrian:
The Cambrian period was the start of what we know of as Earth. It started 541 Million Years Ago and lasted until 485 Million Years Ago. An event at the beginning of the Cambrian occurred called the Cambrian Explosion. The Cambrian Explosion occurred at the beginning of the Cambrian Period. What happened was that many new species suddenly appeared. Scientists are still not sure why so much life came suddenly. One interesting species that came out of the Cambrian Explosion was the Opabina. The Opabina was an arthropod that lived in the Mid-Cambrian seas. It had many eyes atop its head. It used a claw-like limb to grasp food and bring the food into its gut. The Cambrian Period was a cold period of Earth because the continent Gondwana was at the South Pole.
Cambrian:
The Cambrian period was the start of what we know of as Earth. It started 541 Million Years Ago and lasted until 485 Million Years Ago. An event at the beginning of the Cambrian occurred called the Cambrian Explosion. The Cambrian Explosion occurred at the beginning of the Cambrian Period. What happened was that many new species suddenly appeared. Scientists are still not sure why so much life came suddenly. One interesting species that came out of the Cambrian Explosion was the Opabina. The Opabina was an arthropod that lived in the Mid-Cambrian seas. It had many eyes atop its head. It used a claw-like limb to grasp food and bring the food into its gut. The Cambrian Period was a cold period of Earth because the continent Gondwana was at the South Pole.
March 28, 2015
Precambrian:
The Precambrian was a time where it is surprising life even evolved. The Precambrian started with the formation of the Earth and lasted until 541 Million Years Ago. Not much is known about the Precambrian even though it makes up about seven eighths of Earth's history. The reason we know very little about the Precambrian is because rocks from that time period have been what is called metamorphosed (See the article on Metamorphic Rocks in the Geology section for more info) and the fossils and rocks have been messed up, or obscured so much that we can't tell much about the time period. The atmosphere of the Precambrian would have been deadly to life today because it consisted of s lot of Carbon Dioxide and Nitrogen. During the Precambrian an event called the Great Oxygenation happened. What happened was certain organisms were releasing oxygen into the atmosphere. Most organisms at the time breathed other gases and oxygen was harmful to them Over time, the oxygen built up in the atmosphere and the organisms that breathed other gases started dying off. During this time an event called Snowball Earth happened. Earth has had many of these events but the first one happened about 2.2 Billion years ago. The entire Earth became covered in snow, hence the name Snowball Earth. Next time, we will discover the time period after the Precambrian called the Cambrian.
Precambrian:
The Precambrian was a time where it is surprising life even evolved. The Precambrian started with the formation of the Earth and lasted until 541 Million Years Ago. Not much is known about the Precambrian even though it makes up about seven eighths of Earth's history. The reason we know very little about the Precambrian is because rocks from that time period have been what is called metamorphosed (See the article on Metamorphic Rocks in the Geology section for more info) and the fossils and rocks have been messed up, or obscured so much that we can't tell much about the time period. The atmosphere of the Precambrian would have been deadly to life today because it consisted of s lot of Carbon Dioxide and Nitrogen. During the Precambrian an event called the Great Oxygenation happened. What happened was certain organisms were releasing oxygen into the atmosphere. Most organisms at the time breathed other gases and oxygen was harmful to them Over time, the oxygen built up in the atmosphere and the organisms that breathed other gases started dying off. During this time an event called Snowball Earth happened. Earth has had many of these events but the first one happened about 2.2 Billion years ago. The entire Earth became covered in snow, hence the name Snowball Earth. Next time, we will discover the time period after the Precambrian called the Cambrian.
March 22, 2015
Geologic Time:
Over the course of the next few months, we will be taking a look at a concept called geologic time. Put simply, geologic time is the periods of time that make up our Earth's history. You might be able to name a few, the Triassic, Jurassic, and Cretaceous periods for example. However, Earth has been around for 4.6 Billion Years. When you add it all up, there are 12 periods of Earth's history. Since geologic time can be a bit confusing I am going to break things down and tell you how to distinguish between an epoch and a period. The largest way of measuring periods of time is Supereons. There has been only one supereon in Earth's history, which was the Precambrian, but to keep things simple we will classify the Pre-Cambrian as a period. The next way of measuring time is in Eons. Eons tend to last for a half a billion years or more. We are currently in the Phanerozoic era. There have been four eons in the history of Earth. Next, we have eras. Eras last several hundred million years. The time of the dinosaurs was the Mesozoic era. There have been 14 eras in the history of Earth. Next, we have periods. Periods is what I will be basing the articles on. Each article will talk about one period. A period typically lasts between a few dozen million years and around a hundred million years. The last way of measuring time is in Epochs. Epochs last tens of millions of years. Epochs are very small in terms of geologic time and are most commonly used when referring to times after 65 million years ago. In the next couple of weeks, I will talk about the periods of Earth's history. Next week, I will talk about the Pre-Cambrian.
Geologic Time:
Over the course of the next few months, we will be taking a look at a concept called geologic time. Put simply, geologic time is the periods of time that make up our Earth's history. You might be able to name a few, the Triassic, Jurassic, and Cretaceous periods for example. However, Earth has been around for 4.6 Billion Years. When you add it all up, there are 12 periods of Earth's history. Since geologic time can be a bit confusing I am going to break things down and tell you how to distinguish between an epoch and a period. The largest way of measuring periods of time is Supereons. There has been only one supereon in Earth's history, which was the Precambrian, but to keep things simple we will classify the Pre-Cambrian as a period. The next way of measuring time is in Eons. Eons tend to last for a half a billion years or more. We are currently in the Phanerozoic era. There have been four eons in the history of Earth. Next, we have eras. Eras last several hundred million years. The time of the dinosaurs was the Mesozoic era. There have been 14 eras in the history of Earth. Next, we have periods. Periods is what I will be basing the articles on. Each article will talk about one period. A period typically lasts between a few dozen million years and around a hundred million years. The last way of measuring time is in Epochs. Epochs last tens of millions of years. Epochs are very small in terms of geologic time and are most commonly used when referring to times after 65 million years ago. In the next couple of weeks, I will talk about the periods of Earth's history. Next week, I will talk about the Pre-Cambrian.