I am helping my sister with her science homework....?

Question

and we dont know the answers to these questions. if you know the answer to any of these can you let us know.

1.There are two groups of forces that are constantly changing earth's appearance; constructive and destructive.Explain and give examples of each.

2.What evidence is there to support sea-floor spreading?

3.How can the ocean floor keep getting wider but with the earth staying the same size?

4.What is the theory of continental drift?

5. What evidence is there to support Wegener's theory of drift?

6.What is the theory of plate tectonics?

7.How fast are the plates moving per year?

8.What causes the plates to move?

9.Compare and contrast tranform, divergent, and convergent boundaries.

10.What is the difference between active, dormant, and extint volcanoes?

11.Where do volcanoes occur?

12. How are volcanoes and earthquakes related?



if you guys could help us out that would be great, or even if you know a great website to help us!



THANKS!

We did the rest of them but these are the only ones giving us problems!

Answer 1

3. the ocean is below the land and the land floats on the water so the land doesn't move anywhere although the ocean floor gets wider.

4. continental drift it the movement of land masses by convectional currants.

6. plate tectonics is the movement of the earth's crustal plates

7. 1 inch per year

8. convectional currants

11. volcanoes occur in cracks or fissures in the earth's crust.

12. from earthquakes you get volcanoes. when plates move upwards, it forms a mountain and the magma in the earth's crust seeps up through the crack and forms a volcano.

i hope this information helped, i didn't answer some of the questions because i don't feel like typing so much.

but if u really want to know my answer to the questions just let me know. THANK YOU

Answer 2

http://imnh.isu.edu/digitalatlas/geo/basics/platetec.htm
http://en.wikipedia.org/wiki/Sea_floor_spreading

Example of constructive force would be gravity, destructive forces are obvious and in large part are resultant due to tectonics. Earthquakes, Tidal Waves, Volcanic Eruptions.

The two sites listed should help with the rest of the questions

Answer 3

not sure if this will all fit on here but I will try. I am copying this out of a book my kids use. Hope this helps. You may have to read a little but all of your answers should be here...Continental Drift. By looking at a map of the world you will see that Africa and south america seem to fit together. Fossil remains of the same animals have been found on both continents, and both share the same rock formation. Is this just coincidence? A German scientist named Alfred Wegener did not think so. In 1912 he proposed his theory of conitnental drift. According to Wegener, about 200 million years ago all the land on Earth was one large continent that he called Pangaea. Approoximately 180 million years age, Pangaea began to break apart to form three separte continents. The large block to the north ( which later became Europe,Asia, North America, and Greenland) is called Laurasia. It broke away from the toher two land masses, which together were called Gonwanaland. The northern block of Gonwanaland was to become South America and Africa: the southern block would become Antarctica, Australia, and New Zealand. A small piece broke away between the northern and southern parts of gonwanaland and began moving northward. This would be India. These land masses continued to drift. About 65 million years ago, the continents began to look as they do today. South America and Africa had drifted apart, and soon North America and Greenland would break away from Laurasia. India was about to collide with Asia. The southern block of Gondwanaland would soon break apart into seperate pieces, forming Antarctica, Australia, and New Zealand. Although Wegeners theory of continental drift was disbelieved at first, eventually it came to be accepted in a modified form. Increasingly, geologists found goelogical, fossil, and magnetic evidence that the continents were no longer in the same relationship to each other as before. More recently, evidence has turned up to show that the continents themsleves have been built in part from large islands that have drifted and stuck to the continents shorelines. THE MOVING CRUST... Today Earths surface continues to be in motion. According to the plate tectonics theory. Earth's surface - or crust - is broken into pieces called plates. A crustal plate may carry only ocean floor, only continent, or some combination of both. Some plates are huge, such as the Pacific Plate, which carries most of the Pacific Ocean. Others are much amaller, like the Nazca Plate, which lies off the west coast of South America. These plates move around on a layer of loten rock beneath the earths surface much like a boat floats on water. Plates are invovled in three different types of movement. On the floor of the Atlantic ocean, the plates are moving apart in a process called sea floor spreading. The amount of movement is about 2 inches a year, which means that the Atlantic is constantly growing wider, and europe is moving farther away from the United States. As the plates move apart, molten rock wells up from beneath the surface to form a new ocean floor. Sea-Floor spreading in the Atlantic occurs along a huge underwater mountain range called the mid Ocean ridge. Within the ridge is an opening called a RIFT VALLEY, through which the molten rock poiurs out. Rift valleys can be found in other parts of the world too. In East Africa a large rift valley has formed; it may indicate that the African continent is beginning to break apart. The Red Sea may have appeared as a result of the Arabian Peninsula seperating from Africa. In some parts of the world, crustal plates are converging. Here crust is being destroyed, offsetting the new crust being formed in other regions, thereby keeping the earths size from changing.When a plate carrying oceanic crust collides with a plate carrying continental crust, the sea floor sinks beneath the continent, forming a deep ocean trench. Such trencghes are found along Japan and the Aleutian Islands. In these areas volcanoes are common. For example, the volcanic Andes Mountains in South America and the deep trench in the nearby Pacific Ocean may have been produced when two plates converged. The collision of two plates carrying continenetal crust may also lead to the formation of huge mountain ranges. An example is the Himalayas, which were created when India collided with Asia millions fo years ago. when two plates carrying oceanic crust converge, one if forced beneath the other. This results in the formation of an ocean trench accompaied by undersea volcanic activity and earthquakes. Instead of seperating or coming together, two plates may simply move past each other. This type of movement is occurring alondg the San Andreas fault in California.An earthquake is a sudden trembling of Earths crust. Earthquakes generally occur as a result of the movement of crustal plates. The crust cracks along a fault line, which is at the boundary between two plates. As the crust moves apart, rocks on either side bend until they finally break, creating the vibrations that are called earthquakes.Volcanic activity occurs along the boundariues between two plates, just as earthquakes do. In fact, surrounding the Pacific Ocean, in the same area as the earthquake belt is a circle of volcanoes that is called the "Ring of Fire'. When crustal plates come together, one plate often sinks, formong a deep osean trench. The material in this plate is heated by the high tempereatures found within the earths interior and transformed into a molten substance called magma.. Pressure exerted on the magma from above may force it up through a chamber. Eventually the magma may pour out through an opening, or vent, in the earth and flow onto the surface. As the magma pours out, it changes and becomes a substance called lava.... I hope that this helps you to answer at least some of your questions. I know its a lot of reading but at least you will knid of understand it too, just in case the teacher decides to aks you a question, :}

Answer 4

Plates move 1 inch a year, im certian.

Answer 5

Steel comes from Iron.

Answer 6

Is that every question on her homework? You might want to help your sister with listening skills rather than homework.

Answer 7

Number three is erosion.