Author Archives: Adrian Li

The Never-Ending Winter: The Snowball Earth Hypothesis

The history of the planet Earth will always be a mystery that many geologists strive to figure out. In one of my earth and ocean science courses this semester, we talked about the possibility of a Snowball Earth. When I first heard the name, Snowball Earth, I was confused as to what a snowball earth is and why scientists call it that but as the professor began explaining the concept, it became clear.

The Snowball Earth Hypothesis suggests that based on the rock record, the Earth was mostly or entirely covered by ice at certain points over a period of billions of years. Throughout most of the continents today, geologists have found dropstones which are a type of glacial deposits that suggest the presence of ice.

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Glacial Dropstone Source: Michael C. Rygel (WIkimedia Commons)

Dropstones are formed when glaciers move across the land and scratching the surface resulting in the collection of rock pieces. These pieces then combine together and are eventually dropped as the ice melts onto land or into the ocean and are eventually covered by sediments and turned to rock. As these dropstones form, the magnetite particles in the stones reflect the direction of the magnetic field. As a result, geologists have concluded that some of these glacial dropstones were formed at the equator.

Although hard to believe that the Earth can be covered in ice, several factors may have enabled the Earth to be cold enough to have ice at the equator. The first factor was that the sun was not emitting as much energy in the past and therefore the Earth was receiving less heat. Secondly, due to intense rainfall, the CO2 in the atmosphere are drawn down by the rain due to chemical weathering leading to a drop in temperatures.

Quelccaya_Glacier

Quelccaya Glacier Source: Edubucher (Wikimedia Commons)

As temperatures drop, the polar ice caps start advancing towards the equator. As the amount of ice increases, the albedo effect becomes stronger leading to lower temperatures. At this point, I was thinking, how does this make sense since we are not living in igloos today? Well, the answer to that are volcanoes.

Mahameru-volcano

Mahameru Volcano Source: Jurema Oliveira (Wikimedia Commons)

Due to the heat generated by the magma, volcanoes are able to melt through the ice and release many types of gases into the atmosphere such as CO2 and methane. These gases are important because they trapped heat and led to the end of the Snowball Earth. Therefore, over millions of years, these gases accumulated and eventually, the planet was hot enough to melt the ice within thousands of years.

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Source: Big History Project (Youtube Creative Commons)

Although not all scientists believe in the Snowball Earth, I found this theory to be a good example of what science is about. By looking at rocks underneath the ground and with the knowledge about how certain types of rocks form, geologists were able to hypothesize such an extreme event that occurred before humans walked the planet.

Adrian Li

Is that a new tortoise or an existing tortoise?

According to scientists, there are millions of organisms that have yet to be discovered. While many newly discovered organisms are insects, other organisms such as mammals, reptiles and birds are more rarely discovered. But, where do these undiscovered organisms live? Most of these unknown organisms may live at the bottom of ocean trenches or in remote parts of the world that have not been explored yet; however, can undiscovered organisms live among existing organisms that scientists have simply overlooked? Well simply, yes.

Map of Galapagos Island Source: Storpilot (Wikimedia Common)

Map of Galapagos Island
Source: Storpilot (Wikimedia Common)

The Galapagos Islands are a collection of islands that is home to many species of birds, land animals and sea creatures, most notably the finches that Charles Darwin observed. Additionally, the Santa Cruz Island, part of the Galapagos Islands, is home to two tortoise populations that live on the east (Cerro Fatal) and west (Reserva) ends of the island. For many years, scientists believed that the two populations were from the same tortoise species, but recent studies show that they are two distinct tortoise species. This is exciting because as previously stated, new species of organisms, other than insects, are rare; but when new species are discovered, a lot of new information can be gained from studying the unknown organism.

Tortoise Source: Chad Sparkes (Flickr Commons)

Tortoise
Source: Chad Sparkes (Flickr Commons)

Now, what are tortoises and how are they different from turtles? The definition for what constitutes a tortoise from a turtle differs depending on the country. Turtles and tortoises are a part of the Testudines order. In America, turtles are members of the order Testudines that live in freshwater and marine environments primarily. On the other hand, tortoises, by definition, live exclusively on land. Some morphological differences are that turtles have a streamlined shell and webbed feet to navigate marine environments, while tortoises have an arched shell and clubbed feet to help them survive on land.

Turtle Source: Michael Menefee (Flickr Commons)

Turtle
Source: Michael Menefee (Flickr Commons)

In their study, Nikos Poulakakis, Danielle L. Edwards and their team tested and compared the genes of the two tortoise populations located on the Eastern and Western parts of Santa Cruz Island that are believed to be one species, Chelonoidis porteri. To their surprise, the analysis revealed the two populations to be distinct from one another, thus creating a new species of tortoise for the Cerro Fatal tortoises, C. donfaustoi. Although many of the differences between the two species of tortoises are contained in DNA, the Reserva tortoises are on average, larger in body size, shell size and head opening than the Cerro Fatal tortoise.

As a result, new organisms can be found in many different places. Even organisms that were once believed to be a member of an existing species can become a new species as our technology and knowledge of different species increases. Who knows what new organism people will discover next?

Adrian Li