212.Mount Pelee. -At the north end of the island of Martinique in the West Indies rose a conical-shaped mountain. In a hollow bowl- like depression at the top lay a beautiful little lake some 450 feet in circumference. The mountain and lake were pleasure resorts for the people of the city of St. Pierre. According to legend this mountain had been violently eruptive, but in historic time there had been no indica- tion of this except one night in 1851 when the volcano had grumbled and a slight fall of volcanic ash was found in the morning over some of the surrounding region.
On April 25, 1902, people began to see smoke rising from the vicinity of the mountain and from this time on till the final catastrophe smoke and steam came out in small quantities. By May 6 the volcano was in full eruption. On the morning of May 6 the cable operator at St. Pierre cabled, "Red-hot stones are falling here, don"t know how long I can hold out." This was the last dispatch sent over the cable.
About 8 o"clock on the morning of the 8th a great cloud of incandescent ash and steam erupted, swept rapidly down the mountaintoward St. Pierre and in less than three minutes killed 30,000 people, set the city on fire and destroyed 17 ships at anchor in the harbor. Thus within two weeks from the time of the first warning a rich and densely populated region was made a desolate, lifeless, fireswept desert.
213.The Azores. -About 800 miles west of Portugal rises fromthe depths of the Atlantic a group of nine islands, the Azores. They have an area of about 1000 square miles, and the soil is very fertile. The islands are mountainous, one of the mountains rising to between 7000 and 8000 feet above the sea. Like other lofty islands of the deep ocean these are volcanic. Although at present not actively eruptive they abound in hot springs and have frequent earthquakes.
Volcanic cones are abundantly scattered over the islands, andcomparatively fresh lava flows are not wanting. In recent times smallSAN MIGUEL HARBOR IN THE AZORES.
Notice the volcanic cones in the distance.
islands have arisen in the group and eruptions have taken place. There are no other islands near them. Their formation is due entirely to volcanic forces. Islands of this kind and coral islands are the only projections rising to the surface from the deep ocean floor.
214.Volcanoes of the United States. -In the Cordilleran region of the United States, west of the meridian of Denver, there are a score or more of lofty peaks which show conclusive evidence of volcanic ori-gin. Until the summer of 1914 when Mt. Lassen suddenly began to erupt, none of these had been active since white men became familiar with the region. Some of the cones have been so recently formed that the forces of erosion have not had time to wear them away extensively. Thus they are almost perfect in shape like Mt. Shasta. Others, like Mt. Hood,have been deeply eroded, but not
MOUNT LASSEN IN ERUPTION.
This volcano, after being dormant for centuries, suddenly renewed its activity in 1914.
sufficiently to obliterate the coni- cal outline.
In the region around Mt. Taylor erosion has progressed so far that only the roots of the volcanoes still remain, the cones having been entirely worn away and only the central plug of lava left, formingMOUNT HOOD.
A beautiful old volcanic cone.
what is called a volcanic neck. In the Aleutian Islands are numerous volcanoes which are still active, and in Hawaii are some of the greatest volcanoes on the earth.
In Crater Lake we have a volcano whose normal development has been interrupted by an accident, its summit having fallen in, leavingVOLCANIC NECKS NEAR MOUNT TAYLOR.
a circular depression in the top of the mountain surrounded by steepwalls and now nearly filled with water. Except for the water filling, thisCRATER LAKE.
LAVA FLOW IN THE HAWAIIAN ISLANDS.
Liquid lava flowing over a cliff.
A HAWAIIAN CRATER.
decapitated volcano or caldera quite closely resembles the probable condition of Vesuvius before the eruption of 79 A.D.
215.Life History of a Volcano. -A volcano is simply a place in the earth"s surface where molten rock or fragmental material from within the earth is extruded. If the extrusion of the lava is accompa-nied by gaseous explosions, it will be blown into fragments which will fall around the vent and build up a steep-sided cone, like that of Monte Nuovo. If the eruption is less violent, lava may flow from the crater or pour from openings formed in its sides.
As the same volcano usually ejects both the fragmental and molten material, volcanic cones are generally complex in their composition. Sometimes, however, cones are found which are composed entirely of one sort of material. Those which are largely or entirely formed of lava have a much gentler slope than the others. Such are the great Hawaiian cones.
Some volcanoes, like Stromboli, are in constant eruption; others, like Etna, vary their eruptions with irregular periods of rest, while still others remain quiet for very long periods and then suddenly breakCROSS SECTION OF A LAVA FLOW.
forth with terrific force, as did Vesuvius in 79. As a rule, but not always, eruptions are preceded and accompanied by earthquakes. Just why volcanoes erupt is unknown.
After a volcanic cone has come into being it is subject to the action of the erosive forces, and unless its material is renewed byfresh outpourings it will in time be worn down. Unlike other kinds of mountains it is also liable to disruption by explosions from within.
216.Distribution of Volcanoes. -The number of active volcanoeson the earth is about 300. Most of them are situated on the borders of the continents, on islands near the continents, or else they form islands in the deep sea. Soundings show that there are many peaks in the sea which have not reached the surface; these are probably volcanic. Few volcanoes are far from the sea although there is an active crater in Af- rica several hundred miles from the Indian Ocean.