Watch the video and then, there are 4 parts in my upload, writen by my classmates, please make reply(comment) for each paragraph, each reply should around 100 words, this is dicussion homework, so you dont have to write too much. Four thoughtful, responses to the postings. and do not copy from other websites .
1. Despite the age of current seafloor rocks, what evidence suggests that the oceans once existed billions of years ago?
In my opinion, the sediment in the ocean can also suggest the age of the oceans. For example, Rivers, streams, and winds deposit twenty billion tons of sediment from the land into the ocean each year. Due to this information, we can calculate how much sediment in the oceans and estimate the age of the oceans. Although the age of the ocean floor roughly corresponds to the amount of sediment accumulation, dating the seafloor and its sediments is not a good way to estimate the age of the Earth.
2. Turbidity currents are flowing streams or currents of water that is carried with many sediments and picks up sediments as it goes along. With this increased sediment, it also increases in mass and increases in speed. With an increased amount of speed, the friction that is on the bottom of the ocean floor is going to take a longer amount of time to bring this current or sediment to a halt. If a turbidity current was initiated on a large hill of the ocean, gravity will accelerate that downwards, picking up more sediment and giving it more velocity to continue for a longer distance. This is kind of like how it takes a car longer to stop with the same amount of brake pressure when a car is going 60 mph rather than 20mph. Higher velocities take longer to stop or slow than slow velocities.
3. A turbidity current could of moved that large of a distance if it was caused by a earthquake. As mentioned in the textbook an earthquake can cause currents to travel at a speed of 50mph. So it wasn’t because of a lack of friction that caused the speed. I think of the domino effect and the longer it keeps going the quicker it picks up speed. I tried to google a visual example to better understand and one of the useful ways it’s describes is an “underwater avalanche”
4. Despite the age of current seafloor rocks, what evidence suggests that the oceans once existed billions of years ago?
Despite the continental crust being placed at approximately 4 billion years old, the oldest seafloor rocks are thought to have only been around for about 200 million years. However, there is evidence to suggest the oceans are not relatively new to earth. Fossils containing marine animals have been discovered and date back at least 670 million years. Even more impressive, stromatolite (a type of old algae) fossils can be dated back as far as 3.5 billion years, which is more on-par with the age of the rest of the earth.