Ch 25`
Terms
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- A very accurate way to date living and non-living material using the predicted decay of certain elements is called ____________
- Radiometric dating
- The element ______________ is often used for dating very old objects like the Earth, because it has a half-life of over 4.5 billion years
- Uranium
- The__________ is a part of Earth's history when the planet was constantly bombarded with meteors and the srface was liquid rock
- Magma ocean
- The __________ catastrophe occurred when the heavy elements suck to the core of early earth
- Iron
- The magnetic field of Earth protects us against the __________which is radiation given off by our sun
- Solar wind
- The collision between Earth and a Mar's sized planetoid created our _________
- moon
- Two sources of the water on our planet are likely from _________ and ________.
- Volcanoes, comets
- Early life on Earth is hypothesized to be similar to life surrounding ___________ in the deep oceans, where energy from hydrogen sulfide is used
- Hydrothermal vents
- The amount of oxygen in our current atmosphere is a result of billions of years of photosynthesis by ____________
- cynanobacteria
- Evidence suggests that Earth and the _________ _________ were formed at the same time
- Solar System
- In radiometric dating scientists determine the amount of time required for _____ of radioactive element to be converted into product
- 1/2
- ___________ has a 1/2 life of 5703 years, which makes it suitable to date _________ samples
- Carbon-14, young
- Earth's liquid iron core flows and rotates gave rise to the _______ ________, which protects us from solar winds.
- Magnetice field
- The first life on Earth lived in a very hostile environment, where bacteria survived only deep below the surface by extracting chemical energy from ________ _________
- Hydrogen sulfide
- The atmosphere on Earth reached __________ oxygen about 560 million years ago
- 21%
- Briefly discuss 3 major events that took place BEFORE the development of life on Earth. For each event, give some details about what took place and any ramifications for life.
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Iron catastrophe: The surface temperature of the early Earth reached very high temperatures from meteoroid and asteroid bombardment and the radioactive decay of rocks. The surface of the Earth was filled with magma, and the heavy elements, such as iron, sank in the magma ocean to form the iron core of the Earth. This liquid iron core flows and rotates to generate the magnetic field that forms the north and south poles. Without this magnetic field, life would not be possible on Earth. This magnetic field acts as a shield to deflect the solar wind, protecting life from large doses of radiation.
Moon formation: The hypothesized formation of the moon states that a collision between a Mars-sized plant and Earth resulted in the formation of our moon. The impact of the collision was so large as to cause the axis of the Earth to tilt, causing the seasons on our planet. This collision is of obvious importance to Earth’s climates and seasons and to the diversity of life that exists due to these seasonal variations.
Ocean formation: All the water on the planet formed after the planet cooled. The water came from two likely sources, Earth’s volcanoes and from liquid water is comets. Volcanoes produce steam (water vapor) when they erupt. When the Earth was young, it was regularly bombarded by comets. The ice in the comet’s tails would have melted upon contact with the Earth and could have contributed significantly to Earth’s liquid environment. - Describe where the oxygen came from in our atmosphere and give 2 pieces of evidence for this process. How long did this process take?
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By producing oxygen as a byproduct of photosynthesis, early bacteria caused a buildup of oxygen in the atmosphere, which allowed for the evolution of complex plants and animals. The modern day equivalents of these ancient life forms are the blue-green bacteria or cynanobacteria.
The photosynthetic microorganisms coated the surface of rocks in shallow bays, and they secreted a layer of sticky substance to use as protection against ultraviolet radiation. When sediments infiltrated into the layer, the microorganisms migrated to the surface. As this process occurred over hundreds of years, rock-like structures, known as stromatolites, were formed. These stomatolites can be found as fossils, suggesting they were responsible for the oxygenation of the atmosphere.
Iron oxide (or iron ore), which is mined today for steel production, is a byproduct of the oxygenation of the planet. It took about 1.5 billion years of continuing accumulation of atmospheric oxygen to reach the current atmosphere oxygen concentration of 21%.
This process took about 1.5 billion years to raise oxygen levels from about 1% to the current 21% - When the Apollo astronauts brought back moon rock samples they were surprised to find that the compostition was very similar to the rocks found on Earth. Describe the hypothesis that the scientists come up with to explain how the moon was formed, discuss
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Hypothesis: Moon was formed by a collision between early Earth and another small planet. The collision destroyed the other planet and removed a significant proportion of Earth. The debris that was strewn into space eventually coalesced and formed the moon.
The force of the impact caused the Earth axis to be tilted 23*. This tilt gives rise to the seasons and climate found on Earth.
Since some of the debris were of Earth’s origin that it is not surprising that the composition of the rocks on the moon are very similar to that of Earth’s.