32 PHYSICAL GEOGRAPHY. REVIEW QUESTIONS. ——-0£0400—_. The Heated Interior. Enumerate the proofs that the interior of the earth is still in a highly-heated condition. Name some circumstances which render it probable that the earth was originally melted throughout. What is the average rate of increase of temperature with descent below the surface ? How can it be shown that the whole interior of the earth is filled with highly-heated matter? Why is it so difficult to assign a definite limit to the thickness of the earth’s crust? Is the interior of the earth supposed to be in as fluid a condition as that of the lava which escapes from a volcano? What four classes of effects are produced in the crust by the heated interior? Voleanoes. What are volcanoes? What connection have they with the interior of the earth? How do active volcanoes differ from those which are extinct? Explain the origin of the conical form of volcanic mountains, Which generally produces the more destructive effects, ashes or lava? Why? Enumerate the materials which are ejected from the in- terior of the earth through the craters of volcanoes. What is tufa? How is it formed? Which has the greater inclination, a lava-cone or an ash-cone ? Explain in full the manner in which the shrinkage, or contraction of the earth on cooling, produces a pressure both in the interior and in the crust. By what forces are volcanic eruptions produced? Into what two classes may all volcanic eruptions be di- vided? How are those of each class caused? Give an example of each of these classes. What is the highest volcano in the world? Under what five regions may all the volcanoes in the world be arranged ? In what parts of the world are volcanoes most numer- ous? Why are volcanoes more numerous here than elsewhere? Name some of the regions of submarine volcanoes. Why are all volcanoes found near the coasts of the con- tinents or on islands? i What are mud volcanoes? Solfataras? Earthquakes. What are earthquakes? Into what two classes may they be divided ? Name some facts that have been discovered about earth- quakes. ‘ n Name three kinds of earthquake motion. Which is the most dangerous ? Describe the sounds which accompany earthquakes. What is the main cause of earthquakes? To what other causes may they be attributed? What facts have been discovered respecting the pericd- icity of earthquakes ? Give a short description of the earthquake which de- stroyed the city of Lisbon. Are any portions of the earth free from earthquake shocks? In what parts of the earth are earthquake shocks most frequent ? What are dykes? How were they formed? Enumerate some of the gradual changes of level which are now occurring in the crust of the earth. By what are these changes caused ? MAP QUESTIONS. —-059300——. Trace on the map the five principal volcanic districts of the earth. Which contains the greater number of volcanoes, the Atlantic or the Pacific shores of the continents? Does the eastern or the western border of the Indian Ocean contain the greater number of volcanoes? Name the principal volcanic islands of the Atlantic. Of the Indian. Of the Pacific. Locate the following volcanoes: Hecla, Pico, Kilauea, Sarmiento, Llullayacu, Egmont, Cosiguina, » Teneriffe, Antisana, Kilimandjaro, Demavend, Peshan, Osorno, Ere- bus, and Terror. . y->Name the principal volcanic mountains of North America, In what part of the Atlantic Ocean are submarine erup- tions especially frequent ? Name three noted volcanoes of the Mediterranean Sea. Name the portions of the earth which were shaken by the earthquake of Lisbon. When did this earthquake occur? What noted volcanoes are found in the region visited by the earthquake of Lisbon? 3 In what portions of the Eastern Hemisphere are earth- quake shocks especially frequent? In what portions of the Western Hemisphere?