Please help me I cannot find the answer for this Earth Science Question.?
824678
I think you are referring to *trenches*, or more specifically *submarine trenches*.  For example, the Mariana Trench is a submarine trench located in the Pacific Ocean, just east of the Mariana Islands.   \n\nAs you probably already know, it is the deepest part of the earth's oceans, and the deepest location of the earth itself.  It was created by ocean-to-ocean subduction, a phenomena in which a plate topped by oceanic crust is subducted beneath another plate topped by oceanic crust.\n\nCounting the distance from the bottom of the trench to the top of Mt. Lam Lam on the neighboring island of Guam would make Mt. Lam Lam taller than Mt. Everest.  Inhabitants of Guam like to call Mt. Lam Lam the tallest mountain in the world (tongue in cheek, of course).
988673
The generally accepted age for the Earth and the rest of the solar system is about 4.55 billion years (plus or minus about 1%). This value is derived from several different lines of evidence.\n\nUnfortunately, the age cannot be computed directly from material that is solely from the Earth. There is evidence that energy from the Earth's accumulation caused the surface to be molten. Further, the processes of erosion and crustal recycling have apparently destroyed all of the earliest surface.\n\nThe oldest rocks which have been found so far (on the Earth) date to about 3.8 to 3.9 billion years ago (by several radiometric dating methods). Some of these rocks are sedimentary, and include minerals which are themselves as old as 4.1 to 4.2 billion years. Rocks of this age are relatively rare, however rocks that are at least 3.5 billion years in age have been found on North America, Greenland, Australia, Africa, and Asia.\n\nWhile these values do not compute an age for the Earth, they do establish a lower limit (the Earth must be at least as old as any formation on it). This lower limit is at least concordant with the independently derived figure of 4.55 billion years for the Earth's actual age.\n\nThe most direct means for calculating the Earth's age is a Pb/Pb isochron age, derived from samples of the Earth and meteorites. This involves measurement of three isotopes of lead (Pb-206, Pb-207, and either Pb-208 or Pb-204). A plot is constructed of Pb-206/Pb-204 versus Pb-207/Pb-204.\n\nIf the solar system formed from a common pool of matter, which was uniformly distributed in terms of Pb isotope ratios, then the initial plots for all objects from that pool of matter would fall on a single point.\n\nOver time, the amounts of Pb-206 and Pb-207 will change in some samples, as these isotopes are decay end-products of uranium decay (U-238 decays to Pb-206, and U-235 decays to Pb-207). This causes the data points to separate from each other. The higher the uranium-to-lead ratio of a rock, the more the Pb-206/Pb-204 and Pb-207/Pb-204 values will change with time.\n\nIf the source of the solar system was also uniformly distributed with respect to uranium isotope ratios, then the data points will always fall on a single line. And from the slope of the line we can compute the amount of time which has passed since the pool of matter became separated into individual objects. See the Isochron Dating FAQ or Faure (1986, chapter 18) for technical detail.\n\nA young-Earther would object to all of the "assumptions" listed above. However, the test for these assumptions is the plot of the data itself. The actual underlying assumption is that, if those requirements have not been met, there is no reason for the data points to fall on a line.\n\nThe resulting plot has data points for each of five meteorites that contain varying levels of uranium, a single data point for all meteorites that do not, and one (solid circle) data point for modern terrestrial sediments. It looks like this:\n\n\nPb-Pb isochron of terrestrial and meteorite samples.\nAfter Murthy and Patterson (1962) and York and Farquhar (1972) .\nScanned from Dalrymple (1986) with permission.  \n\nMost of the other measurements for the age of the Earth rest upon calculating an age for the solar system by dating objects which are expected to have formed with the planets but are not geologically active (and therefore cannot erase evidence of their formation), such as meteorites. Below is a table of radiometric ages derived from groups of meteorites:\n\n\n--------------------------------------------------------------------------------\n \nType Number\nDated Method Age (billions\nof years) \n\n--------------------------------------------------------------------------------\n \nChondrites (CM, CV, H, L, LL, E) 13 Sm-Nd 4.21 +/- 0.76 \nCarbonaceous chondrites 4 Rb-Sr 4.37 +/- 0.34 \nChondrites (undisturbed H, LL, E) 38 Rb-Sr 4.50 +/- 0.02 \nChondrites (H, L, LL, E) 50 Rb-Sr 4.43 +/
932795
The 'science guru' is right, but I'll chime in to try and help you wrap your mind around it. \nThe slower magma cools the bigger the crystals in it get. The deeper the magma is in the earth the more it is insulated (like a pizza in one of those pizza delivery bags) and so it cools lots slower the deeper it is.\nThe faster the magma cools the smaller the crystals in it. Since the earth insulates the magma it has to get closer to the surface before it can cool fast enough to have small crystals.\nIf you have two different sizes of crystals then you must have two different rates of cooling.\nThe crystals that can form at higher temps start forming first, of course, and then, when the magma gets pushed up nearer the surface the rest of the material cools quickly into small crystals that surround the larger ones.\nDoes that help?
500218
The correct answer is C.  This is referred to as the rheological division of the mantle, as opposed to the chemical division (which puts the mantle into reservoirs such as MORB, HIMU, etc.)  The lithosphere behaves rigidly wheras the asthenosphere behaves plastically.
874879
About 1,800 miles beneath the surface, Earth's internal structure changes abruptly where the solid rock of the mantle meets the swirling molten iron of the outer core. \nBut the boundary between the core and the mantle may not be as sharply defined as scientists once thought. By analyzing earthquake waves that bounce off the core-mantle boundary, researchers have found evidence of a thin zone where the outermost core is more solid than fluid.\n\nThe existence of such "core-rigidity zones" -- small patches of rigid material within the fluid outer core -- has been suggested before, but this report marks the first time scientists have detected one.
72511
the earth was at a stable orbit.  no  tilt or axis to cause differences in the seasons the earths temperature was just about uniform at 72 deg F.  the earth was at that tome also protected by the vapor barrier basically A thin shield of ice in the uper atmosphere that served 2 purposes it blocked out the harmful ultra violet radiation from the sun  and it increased the atmosphereic pressure to 2 atmospheres.\n\nthis caused things to live a lot longer and grow a lot bigger.  plants for one thing.  there is more coal on the earth right now then there are plants to produce it.  meaning if you were to take all the plants on earth right now and turn them into coal the pile of coal that you could make would be less than that currently available in the ground not including what has already been taken out.\n\nplanys grew much taller in this environment and so did reptiles lets take the crocodile.  a croc now a days can live about 100 years.  reptiles throughout thier life never stop growing.  so now you have an animal that in 100 years can grow to be about 15 feet long but instead you give it 900 years to grow.....presto you have a dinosaur.  \nthen a few thousand years ago an ice meteor crashed through the vapor barrier hitting the earth. this caused the barier to colapse and as it fell it began to melt and other various things and the world was covered in a great flood.  the earth finally settled back out into a somewhat normal rotation (you ever seen what happens to a gyroscope when you bump it)\n\nnow the earth has a 27.3? or is it 23.7 deg tilt to its rotation that causes us to have 4 seasons and tropics temperate zones and artic zones.\n\nBTW the earth is between 6000 and 10000 years old SCIENCE CAN PROVE IT.  if you want to know how just ask me.  i'll try to explane it as best as i can or you can wisit this website.  and do some reading\n\nall the SCIENCE is right there.
787294
Try Wikipedia, or perhaps your local library has a general Geology book that you can reference
375320
a) Earth's surface is made up of about a dozen enormous slabs, or plates. The slow movement of these plates across the surface is called continental drift, or plate tectonics. \n\nb) the outermost level of the land or sea; "earthquakes originate far below the surface"; "three quarters of the Earth's surface is covered by water" \n\nc) Is a kind of layer  (a relatively thin sheetlike expanse or region lying over or under another )
71958
muromets is correct. You can model this yourself using clay. On a cookie sheet, put a half inch of water. On top, put a 1/2 layer of rolled clay. This is what the earth was liked pre-flood. The earth was watered from below. Now break open the center and the water will burst forth (as Genesis describes) and now the clay is covered by the water as the clay sinks. Now pull the clay out toward the corners and the water will display into seas.\nIn order for the continental drift to occur properly, the earth would have had to expand, thus making physics of the covering of the earth with water and its later displacement to be quite possible.
317463
When liquid magma comes out of the earths crust at the mid-oceanic ridge, it cools rapidly forming crystals. These crystals have magnetic properties that align the crystal according to the earths magnetic field at the time they cooled, similar to how a compass needle points north, the magnetism in the crystal indicates which direction was north when the crystal was formed.\n\nHowever, the direction that is north today, was not always north in the past, in fact many times in geologic history, the north and south poles were reversed entirely. This is reflected in the "magnetic bands" found in rock on the ocean floor.\n\nSo, if you imagine the Atlantic Ocean between the U.S. and Europe, there is a mid-ocean ridge between the two. If the plates never moved, then the magma coming out of this ridge would just pile up, but instead, this is the "engine" that moves the plates away from one another. As you move from the mid-ocean ridge towards the continents, the crystals in the rock have different magnetic orientations that show these flip-flops of the earths magnetic field through geologic history. Because this material originated at the mid ocean ridge, but is now closer to the continents, it shows that the earths crust, the floor of the ocean, is moving AWAY from the mid-ocean ridge and TOWARDS the continents.\n\nThere are a lot of  diagrams that would probably help you understand this better. CHeck out a geology book, or look online.\nGood Luck!
513176
Try http://googleearth.com\nMaster.
898375
I know the answer is in my basic physics book.  I would have to look it up.  You should too.
467280
Try the www.usgs.gov, it is the US geological survery website they have all kinds of information on things like that.  If the info you want isn't there there will probably be a link that you can find for that information.
761593
Probably silicone and iron.   It's a friggin big rock.   Hollow it out a bit; near the center the gravity is probably near earths gravity.
1095641
Think of the Earth as a big blue marble. Got it? Ok. Now, think of a layer of bubble wrap around the marble. That would be the air we breathe, or the troposhpere. It is air, so it doesn't weigh much, but it does weigh something. Now think of another layer of bubble wrap on top of the first. That would be the stratosphere. Then another layer, which is the mesosphere, and then another layer, the thermosphere. Now you've got four layers of bubble wrap, on top of each other. Each one is PRESSing down on the ones beneath it, causing PRESSURE. Hope that helps.
473257
Try http://www.geo.lsa.umich.edu/~crlb/COURSES/270/Lec12/Lec12.html\nIt helped me do my homework! Also, it has pictures of plate boundries and plate tectonics. Hope it helps!
344596
Wow, that is a very good and tricky question. If you really want to know please send me an e-mail and I will tell you the most recent answer proposed by the science community.