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Monthly archives: June, 2021

Surface of Lavaflows

The surface texture of lava depends on (i) the temperature of lava, (ii) the composition of lava, and (iii) the velocity of the flow during the eruption. The surface texture of newly consolidated lava-flows are of three types; (1) Blocky Lava: Rhyolitic lavas, because of their high silica content, are usually very viscous. Their movement …

Volcanic Eruptions

Volcanic eruptions are of two types: (i) centeral eruptions, (ii) Fissure eruptions. Central Eruptions: In central eruptions, the emission of lava takes place through a vent. Such a volcano usually exhibits a cone-and-crater arrangement. This volcano may have parasitic cones on the flanks of the main structure. Etna, a European volcano, has more than 200 …

Volcanoes and their types

A volcano is a vent or fissure in the earth’s crust through which hot lava and volcanic gases are thrown out. Volcanic eruptions may be either explosive or quiet. The earth’s upper mantle (asthenosphere), under the crust, is nearly molten. Magma originates at this depth. They migrate upwards, often along faults. In a volcano, the …

Earthquake resisting structures

Controling an earthquake: In an earthquake-prone area if it is known that the strain is accumulating, the threat of earthquakes can be reduced by the following methods. A number of deep hole are drilled along a fault line in which stress has been detected. then water is pumped down into the holes. This water acts …

Prediction of earthquakes

In seismic regions, earthquakes occur frequently and cause loss of life and property. This emphasizes the need for reliable methods of earthquake production. To predict earthquakes it is necessary to detect the fault lines where strains are building up. The following methods are used to locate areas under stains. Read other similar articles In Japan, …

Global distribution of the Earthquakes

Earthquakes occur in geologically active areas, such as mid-oceanic ridges and mountain-building regions. The zones where earthquakes occur frequently are known as ”Seismic belts”. The principal seismic belts on the earth’s surface are as follow: Read more related articles Circum Pacific Belt: This belt encircles the Pacific ocean and more or less overlaps the belt …

How to locate the epicentre of an Earthquake?

The first thing you need to find the location of an earthquake is the recorded seismograms of three differently located seismographs. You will also need a map of the world, a ruler, a pencil, and a compass for drawing the lines for locating the epicenter. Now you can easily find the location of the epicenter …

Earthquake intensity scales

The effect of an earthquake is, generally, stronger near the epicenter and decreases gradually outwards. To have an idea about the intensity of an earthquake in different areas, intensity scales have been devised. The two commonly used intensity scales are : (i) Rossi Forel Scale, and (ii) Richter Scale (1). Rossi Forel Scale: The earthquake …

Origin of earthquakes (Elastic Rebound Theory)

Earthquakes are classified on two bases, one is surface causes, volcanic eruption, and tectonic movement. Among these types, volcanic earthquakes are the most common and disastrous, therefore discussing the tectonic type of earthquakes is very important. The reason behind tectonic earthquakes is the tectonic movement of crustal plates. There are three types of tectonic movements. …

Classification of Earthquakes

Classification I. Depending upon their mode of origin, the earthquakes are classified into the following groups. Earthquake due to surface causes: Earthquakes may be generated by landslips and collapse of the roofs of underground caverns and other surface disturbances. Most of these are very minor, and some are even rarely felt. All causes of an …