Let’s take a deep-sea dive and look at the early life forms that existed in the great phenomenon known as the “Avalon Explosion”. These early life forms can be described as multicellular organisms that differ greatly from what we know today. These organisms challenged what we previously knew about the tree of life.

Why Watch This Video?

  1. Have you ever wondered what the first/earliest fossils look like and how they relate to organisms today?
  2. Would you like to know how the Avalon explosion started and where in the world it was discovered?
  3. Have you ever been confused by how early organisms existed in their geological time period?

Key Terms

The Avalon Explosion: Named after the Avalon Peninsula, where a significant deposit of early life forms was discovered. The Avalon Explosion contains the oldest fossils known in the fossil record and differ vastly from organisms later found in the fossil record.

Multi-Cellular life: An organism that is composed of more than one cell. These multiple cells form tissues and organs such as heart, liver and vessel that hold different functions for the survival of the organism. Multi-cellar life includes all life forms except for bacteria. Bacteria are known as unicellar life which are single-celled organisms.

The Ediacaran Period: This geological time period was named after the Australian hills where geologist Reginald Sprigg found a fossil that launched the history of the Avalon explosion. Ediacaran has geological time period from 635 to 541 million years ago. This time was known for its vast geological and biological change from microscopic organisms to animals.

Loose Ends

The Cambrian Explosion

Originally thought to be the first period that complex organisms appear. It is the first event to host ancestral organisms of the major life groups today. It is also significant due to the massive number of early fossils preserved.

The Cryogenian period

A geological time period that lasted between 720-635 million years ago. This time period was the second-last geological period of the Proterozoic Aeon, ending 541 million years ago with the Cambrian explosion. The Cryogenian period was a dynamic time of rapid evolution of early life. It was also a period of environmental changes which is linked to how the evolution of life grew and survived. The environment is said to be so cold that most modern animals we see today, including humans, would have a difficult time surviving. Atmospheric oxygen levels were half of what is today, but oxygen levels were raised towards the Ediacaran period thanks to the proliferation of photosynthetic multi-cellar life.


Cyanobacteria is a form of bacteria. They are also referred to as blue-green algae. They are considered different from normal bacteria because they contain chlorophyll-a. Cyanobacteria utilize the sun and carbon dioxide for photosynthesis to produce carbohydrates (food) and oxygen. The oxygen produced by the cyanobacteria is thought to oxygenate the ocean to allow the Avalon explosion to occur.

Self-Test Questions

Scroll down for the answers.

1. Which fossil was found in 1957 that convinced geologists to start looking for fossils in rocks that were normally ignored?

  1. Trilobite
  2. Euryarchaeota
  3. Charnia
  4. Tribrachidium

2. Which Pre-Cambrian life forms had traits that were animal like?

  1. Metazoans
  2. Eukaryotes
  3. Archaeans
  4. Protozoans

3. Which fossil is thought to be an ancestor to trilobites?

  1. Kimberella
  2. Spriggina
  3. Cryptozoa
  4. Dickinsonia

4. What did Virginia Tech name the “Avalon Explosion” after?

  1. Reginald Avalon
  2. A fossil found in Canada
  3. Avalon Peninsula
  4. Mistaken Point

5. How did Rangeomorphs grow?

  1. Branching fractally
  2. Branching bilaterally
  3. Branching trilaterally
  4. Branching horizontally


1. C: Charnia. Charnia was 7 centimetres long and had a clear organized structure to prove it was a living thing. It convinced geologists to look at fossils in the rocks they previously ignored.

2. A: Metazoans. All early forms of Pre-Cambrian life seemed to have an alien look to them. However, metazoans appeared later and had animal like traits. For example, “Haootia” which is mentioned in the video (at 3.41). Metazoans are classified as multi-cellular organisms.

3. B: Spriggina. Spriggina was named from Reginald Spriggs who was the geologist mentioned at the beginning of the video. Spriggina had a crescent shaped head and rudimentary sensory organs. Their fossils revealed a whole new chapter to the history of life.

4. C: Avalon Peninsula. The Avalon Peninsula was a Canadian site that preserved so much fossils during that time period.

5. A: Branching fractally. Rangeomorphs resembled Charnia which looked like plants. However, Rangeomorphs were not plants. They resided on the ocean floor which was to deep to photosynthesize. Instead, they absorbed the nutrients from the water. They were not considered animals either, as they grow fractally meaning that each branch looked the same as the whole organism.

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Item Credit: PBS Eons

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