Era Report WAC - 9/22/17

       According to the Geologic Time Scale, there are four major eras in history that shape Earth as we know it today. The Precambrian era is the first era that occurred on Earth. This era covers almost 90% of Earth's entire history. The beginning of the Precambrian era started with the formation of Earth 4.6 billion years ago and ended at the first sign of complex life about 540 million years ago. This era is divided into three eons. This includes the Hadean eon, the Archean eon, and the Proterozoic eon. The Hadean eon started when the planet first began to form as the Earth's core was building. The solar system was constructing within a cloud of dust and gas, known as the solar nebula. The Archean eon was a time of continental building and showed the first stages of early life on Earth. At this time, the Earth's crust cooled enough that rocks and continental plates began to configure. The final eon apart of the Precambrian era is the Proterozoic eon. During the Proterozoic eon, life began to evolve into more complex organisms.

       Since the Earth was barely formed during the Precambrian era, there were little to no plants present during this time. According to the Penn State University department of science, Lichens are believed to have been the first fungi existing on Earth. A Lichen is a composite organism that arises from algae cyanobacteria living among filaments of multiple fungi in a symbiotic relationship. During the Proterozoic eon of the Precambrian era, Lichens teamed up with photosynthesizing organisms. The organisms that Lichens collaborated with, include cyanobacteria and green algae. Together these plants conceivably boosted oxygen levels in the atmosphere high enough for animals to develop skeletons, grow larger, and diversify.

        Toward the end of the Precambrian era, the first life formed. The first one-celled organisms formed during the Archean eon of the Precambrian era. Early evidence of life that was once living in the oceans of Earth were microscopic bacteria that were capable of photosynthesis. These one-celled organisms helped make the air and water around Earth become full of oxygen. Once there was plenty of oxygen in the atmosphere and in the ocean, new life could form. New varieties of bacteria began to harness the power of the sun through the biochemical process known as photosynthesis. This energy source ultimately lead to the creation of simple plants and opened the planet up to animal life. The Precambrian era ended with the emergence of complex, multi celled life forms. By the end of the Archean eon, the ocean floor was covered in a living mat of bacterial life.

         Scientists named this eon after the Greek god Hades, who ruled underworld. The surface of the Earth during most of the Hadean eon must have been like our image of the underworld. During the Hadean eon the Earth released tremendous amounts of heat as the Earth's core was forming, due to gravitational sinking. In fact the surface temperature of Earth at this time, was at 1200 degrees Celsius. Throughout the Archean eon, the outer covering of the Earth cooled and hardened into a crust. The hot molten leaked out at weak places in the crust, creating volcanoes. Water from comets and hydrated minerals condensed in the atmosphere and fell as torrential rain. This rainfall formed and filled oceans. The presence of micro organisms on Earth during this time, indicates that 4 billion years ago the Earth's surface temperature must have cooled to less than 100 degrees Celsius. Furthermore, the oceans must have been above 0 degrees Celsius. Therefore, the Earth's surface temperature was between 0 degrees Celsius and 100 degrees Celsius. These temperatures would have had to occur on Earth during this eon in order for these organisms to have lived.

           The basis of Earth's growth happened during the Precambrian era. There are three eons that make up the Precambrian era, including the Hadean, the Archean, and the Proterozoic. The Earth had just formed during the Hadean. At scorching temperatures, there were an abundance of radioactive elements and collisions with other solar system bodies. Approximately 70% of continental landmass was formed during the Archean eon. Huge pieces of crust began to move in different directions, called tectonic plates. This tectonic activity formed the first continent, Rhodinia, about 1.1 billion years ago. The modern-day continents South America, Australia, and Antarctica surrounded North America which was located in the middle. The Earth's crust started to cool down to between 0 degrees to 100 degrees Celsius for micro-organisms to live. However, the Proterozoic was the time when life actually evolved into more complex organisms. These organisms include bacteria life and multi celled organisms such as the Lichen fungi. All of these events that have occurred billions of years ago, are components that form the Earth we live on today.

The Precambrian Era - 9/17/17

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According to the Geologic Time Scale, there are four major eras in history that shape Earth as we know it. The Precambrian Era is the first era that has occurred on Earth. This era covers almost 90% of the entire history of the Earth. The beginning of the Precambrian Era started with the formation of the Earth about 4.6 billion years ago and ends at the first sign of complex life about 540 million years ago. This era is divided into three eons, including the Hadean, the Archean, and the Proterozoic. The Hadean eon began when planet first began to form, about 4.6 billion years ago. Scientists named this eon after the Greek god Hades, who ruled underworld because during most of the Hadean period the surface of the Earth must have been like our image of the underworld. During this time, the Earth released tremendous amounts of heat (at a surface temperature of 1200 degrees Celsius) as the Earth's core was forming due to gravitational sinking. At the time of the Archean eon, the Earth's crust cooled enough that rocks and continental plates began to form. It was early in this eon that life first appeared on Earth. Our oldest fossils date to roughly 3.5 billion years ago, and consist of bacteria micro fossils. The final eon apart of the Precambrian Era is the Proterozoic eon. During this time, life began to evolve into more complex organisms. The first evidence of life that were once living in the oceans of the Earth were one-celled micro organisms that were capable of photosynthesis. They helped the air and water around the Earth, become full of oxygen.

S&EP - SP6: Constructing explanations and designing solutions

I evaluated information to explain the history of the Precambrian era and form hypotheses. In order to complete the worksheet for this project, much research was required. I needed to search the internet to figure out when the Precambrian era began and when it ended, how long it lasted, the different periods it is divided into, the major events that occurred during the era and its different periods, the climate during this era, the positions of the continents during this period, what types of life lived during this era, and finally the major types of plants present in this era. Once finding the information for each of these topics, I answered the questions on the worksheet using detailed ACE explanations. I constructed an explanation of each topic I researched for the Precambrian era, when I found the needed information by searching sources online and collecting the information using the ACE structure of answering. I designed a solution to a problem when a source I was searching didn't have enough information needed to answer the topic questions. However I solved this problem by researching multiple sources to grasp as much information as I could find on the topic. For example, one website I visited didn't mention anything about plants existing during the Precambrian era. But after researching multiple websites, I finally found a website that gave me all the information I needed on the plants that lived during this era.

The Age of Rocks - 9/10/17

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The Geological Time Scale is a record of the life forms and geologic events in Earth's history. The Geological Time Scale includes the age of rocks or the years since the rocks are formed. There are two ways that geologists determine the age of rocks. The Relative age is the age of a rock compared to the ages of other rocks. For example the rock is younger than the rock beneath it. The Absolute age is the number of years since a rock is formed. For example the rock is one million years old. The law of superposition states that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it. Therefore the older the rock is, the deeper it is in the ground. Another way to determine relative age of rocks is the Cross-Cutting Principle: when "something" cuts across a body of rock, that "something" is younger than the rock it cuts across. 

S&EP - SP7: Engaging in argument from evidence

I use evidence to defend my explanation. I took notes on the age of rocks and fossils providing the power point about how scientists find the age of fossils, as evidence. I formulated evidence based on solid data when I stated that the top layer of rock is younger than the bottom layer of rock, using the fact that the older the rock is, the deeper it is in the ground as evidence. I examined my own understanding in light of the evidence. I used to think that rocks were dated depending on what stage of the Rock Cycle they were in, but because of understanding the information on the power point that my teacher presented in class, now I think that rocks are dated by their layers. I collaborated with my peers in searching for the best explanation. I did some research on the age of rocks and fossils which I discussed with my class and table group. Together we figured out that scientists find the age of fossils depending on how deep the rock is in the ground.