Thread: Homework problems. Answers needed.

1)What percentage of earth lives within few tens of kilometers of ocean?
a)20 b)50 c)80 d)10 e)90
2) new sea floor is created at convergent margins where crust is destroyed(True or False)
3)what percentage of earth surface is below sea level? a)10 b)30 c)70 d)All of earth surface below sea lebel
4) the focus of an earthquake a)is the same thing as the epicenter b) can be located using only one seismograph c) the primary point of rupture in the earth crush d)the point on the earth surface above the fault rupture
5)when one plate subducts underneath another, which of following do NOT form?a)large explosive volcanoes b) deep ocean sea trenches c) mid ocean ridges d) atolls
6)A possible "driving force" for plate motions is: a)volcanic eruption at hot spots b) shifts in earths magnetic field c) convection in the mantle d) the weight of subducted continents pulling downward
7)Do you expect the ocean to mix by the convection? Why or why not?
8)Why is sediment cover extremely thin close to the mid ocean ridge system?
9)If you find sediment that is 40 million years old on the sea floor, what does this tell you about the age of the oceanic crust in this location?
10)Explain how island chain of Hawaii illustrates pacific plate is moving?
11)Why are pillow basalts most common type of rock on earth?
12)what two differences in oceanic crust and continental account for relative difference in vertical positions?

You obviously haven't read this: Homework problem? READ THIS BEFORE POSTING

Originally Posted by sims70

1)What percentage of earth lives within few tens of kilometers of ocean?
a)20 b)50 c)80 d)10 e)90
2) new sea floor is created at convergent margins where crust is destroyed(True or False)
3)what percentage of earth surface is below sea level? a)10 b)30 c)70 d)All of earth surface below sea lebel
4) the focus of an earthquake a)is the same thing as the epicenter b) can be located using only one seismograph c) the primary point of rupture in the earth crush d)the point on the earth surface above the fault rupture
5)when one plate subducts underneath another, which of following do NOT form?a)large explosive volcanoes b) deep ocean sea trenches c) mid ocean ridges d) atolls
6)A possible "driving force" for plate motions is: a)volcanic eruption at hot spots b) shifts in earths magnetic field c) convection in the mantle d) the weight of subducted continents pulling downward
7)Do you expect the ocean to mix by the convection? Why or why not?
8)Why is sediment cover extremely thin close to the mid ocean ridge system?
9)If you find sediment that is 40 million years old on the sea floor, what does this tell you about the age of the oceanic crust in this location?
10)Explain how island chain of Hawaii illustrates pacific plate is moving?
11)Why are pillow basalts most common type of rock on earth?
12)what two differences in oceanic crust and continental account for relative difference in vertical positions?

In this case, Google is your friend, not the science forum.

Originally Posted by sims70

1)What percentage of earth lives within few tens of kilometers of ocean?
a)20 b)50 c)80 d)10 e)90
2) new sea floor is created at convergent margins where crust is destroyed(True or False)
3)what percentage of earth surface is below sea level? a)10 b)30 c)70 d)All of earth surface below sea lebel
4) the focus of an earthquake a)is the same thing as the epicenter b) can be located using only one seismograph c) the primary point of rupture in the earth crush d)the point on the earth surface above the fault rupture
5)when one plate subducts underneath another, which of following do NOT form?a)large explosive volcanoes b) deep ocean sea trenches c) mid ocean ridges d) atolls
6)A possible "driving force" for plate motions is: a)volcanic eruption at hot spots b) shifts in earths magnetic field c) convection in the mantle d) the weight of subducted continents pulling downward
7)Do you expect the ocean to mix by the convection? Why or why not?
8)Why is sediment cover extremely thin close to the mid ocean ridge system?
9)If you find sediment that is 40 million years old on the sea floor, what does this tell you about the age of the oceanic crust in this location?
10)Explain how island chain of Hawaii illustrates pacific plate is moving?
11)Why are pillow basalts most common type of rock on earth?
12)what two differences in oceanic crust and continental account for relative difference in vertical positions?

I won't answer them, but i will tell you what each question is supposed to teach you.

1) The ocean isn't the only source of water, look at rivers as well, however, for larger cities, fresh fish was needed to feed the masses, and to ship in goods via the sea.
2) This question doesn't make sense to me, crust isn't destroyed it simply moves underneath other plates.
3) How much of the earth is below sea level, given a few hiccups (making it 99,9999998% or something), all of it. But the question was, how much of the earth surface. Think about how much water you see when you look at a globe.
4) I have never heard of the difference of a focus, and epicenter, using one seismograph you can locate vibrations in one spot. Depending on if this seismograph also reads in multiple diagonal ways, you can also pinpoint the direction, and an estimate location. However this way is inaccurate and most seismographs are simply a weight in a electromagnetic field, or a proverbial weight on a string.
5) You really have no idea how to answer any of these questions? Why not simply answer the ones you know and let us explain some questions you don't know how to.. Just google all of these phenomena, and see if you can link it to plate "subduction"..
6) etc..

I realise the due date for sims70's homework must be well past and from their post count (1) they have likely never returned, so I thought a couple of comments in response to Zwolver might be useful.

Originally Posted by Zwolver

2) This question doesn't make sense to me, crust isn't destroyed it simply moves underneath other plates.

This is not strictly true. Oceanic plates subducted into the mantle are generally absorbed into the mantle and thus are destroyed.

Originally Posted by Zwolver

4) I have never heard of the difference of a focus, and epicenter, using one seismograph you can locate vibrations in one spot. Depending on if this seismograph also reads in multiple diagonal ways, you can also pinpoint the direction, and an estimate location. However this way is inaccurate and most seismographs are simply a weight in a electromagnetic field, or a proverbial weight on a string.

The focus of an earthquake is the point of origin of the earthquake. The epicentre is the point on the Earth's surface directly above the focus. My seismology is very rusty, but I believe one requires multiple seismographs to pinpoint the focus, essentially by triangulating its position.

I'm quite interested in geology, hence this was the sub-forum I headed for first. It doesn't seen to active. I hope that may change.

Cheers.

i work with geologists as my job, i am technically not really one myself. Their terminology is very unforgiving, and foreign to me.

Geology is a subject not really capturing anyone's imagination really. It doesn't come up with gadgets to keep the masses interested. It doesn't come up with wild solutions on changing anything. It just studies the earth and its systems.

Volcanoes, tornadoes and earthquakes are usually what captures the public's attention. Because their impact is quite instantaneous.

Your rebuttal to my second point is a good one though, but i like to teach ways to come up with facts, not memorizing the facts. Usually in math class, i never studied the formula's, i made them up where i went. Found that to be more effective. Why carry around a flaming torch if you could learn how to make fire anywhere.

With 4, i know that it is usually done by measuring time and vibration in multiple places. The thing with it is, "can be located with only one seismograph", i will try my best to find a way to do this. Not to be as precise as possible. Using one, i believe you can use directional vibration to find out if shock came from north or south. Where on this line it is, how far from the seismograph can be extrapolated using the depth and density of ground layers, and the time and number of each aftershock. As when ground shakes it reflects sound and vibrations through the ground. I think you could also get a pretty good guess of where the epicenter of the quake was. However, this is complicated.

We need to make the whole forum more active though ..