Earth Science

1. Summarize advances over time in determining the age of the Earth, including the importance of the discovery or radioactivity. Herodotus counted layers of earth near the Nile River in 450 B. C. E. The Bible was used in the Middle Ages to compute the age of the Earth. The 18th and 19th centuries brought a more scientific look into determining the age of the Earth by studying the salinities of the oceans, the rates of sedimentation, and models of cooling of different materials in order to calculate the Earth’s age.

In 1862, William Thompson calculated the Earth’s age to be 98 million years and recounted that age to determine that it was actually between 20 and 40 million years old. He used a very thorough method and ended up being wrong on both counts because he was unaware of the existence and effects of radiation. There was another method of aging the Earth utilizing the relative positions of rock layers. Ensuring that unconformities were accounted for, that fossils were used as benchmarks, and understanding what rocks are older than others, this relative aging helped to develop a geologic time scale.

The discovery of radioactivity allowed scientists to understand heat better. The radioactive decay of elements helps scientists calculate the age of an object by using the statistics of large numbers. 2. What makes Earth a habitable, relatively stable environment within which we exist and survive? Review the early development of the solar system, including the Big Bang theory, to support your answer. At the time of the Big Bang, an unimaginable cataclysm released helium and hydrogen. Soon after the Big Bang, energy began converting into matter.

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Large clouds of this matter began attracting to other particles which formed everything, including our Solar Systems. The beginning of the Solar System started with a cloud of gas, dust, and ice particles. Gravity acted on the cloud, drawing it into itself and reducing its volume. This occurrence would have caused the Solar System to shrink and rotate as it was drawn into itself. Due to angular momentum, the spin would have gotten faster and faster over time. Gravity and centripetal force are fighting against each other to maintain celestial bodies in an orbit around the Sun.

The 1% of the mass in our Solar System that didn’t get sucked into the Sun is what makes up our planets, asteroids, and moons. The centripetal force acting on the planets aligns them with the Sun’s equator and creates the mostly flat orbit of the Solar System. 3. Alfred Wegener was a polar explorer and visionary. Describe how his early work was viewed with skepticism and how ultimately his theory on continental drift was proven. What kinds of evidence did Wegener rely on to substantiate his continental drift hypotheses (Pangaea)? He was viewed as a meteorologist and not a geologist.

With no real geological knowledge, he formulated the continental drift theory was due to tidal pull from the Sun or centrifugal force. Because scientists of the time couldn’t believe that continents could float through rock as if it were liquid. We now know that due to convection that we see through seismic tomography that the Earth is a kind of liquid on which the lithosphere is floating. His basis was partly due to the edges of the continents fit together as a puzzle. Also, rocks, plants, and animals that were spread across the globe must have started together because a rock didn’t swim to its new location. . Explain how seismic tomography has been used to show what is actually happening on Earth. Include in your answer a discussion of plate tectonics and sea-floor spreading. Like having an MRI of your brain, seismic tomography allows scientists to see the results that sound waves report when they bounce back from colder rock and warmer rock. This report shoes the convection of heat and rock that is occurring inside the Earth. This convection makes its way to the surface of the Earth which shifts the plates at the weak points.

This moves those plates with sometime violent and dangerous results. The plates “ride” on more unstable parts of the Earth’s asthenosphere. The subduction zones allow rock to be moved downward as warmer rock moves up. 5. Explain how the laws of thermodynamics determine the motions that result in the formation of mountains and oceans. 1st law: Energy can be moved from one form to another but cannot be created or destroyed. This allowed for matter to be created from energy which was a preamble to the creation of the Solar System and most of the Universe; including mountains and oceans. nd Law: Energy of an object at the initial state is greater than then energy of that object at any other time; provided no new energy is introduced to the object. This law is the reason the conveyer belt theory works. Rocks on the mountains are washed to sea by water that was evaporated from the oceans to create rain which runs back out to the sea (carrying rock) to the subduction zones that will sink to the core which will heat the rock which will move to the colder area (the surface of the planet) causing a violent movement which pushes plates into each other creating more mountains. Lecture, Michael Wysession, 2008.

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