Craters A bowl-shaped pit or crater is found at the summit of most volcanoes, centered over the vent. During an eruption, the lava blasts or flows out of the vent until the pressure below is released. The lava that is at the tail-end of the ...Source: McGraw-Hill Professional
Eruption Signals Volcanoes are fairly “iffy.” If we look at all the recorded eruptions over the centuries, we would find that some smoldered for months to years, while others gave no notice at all before belching out with deadly ...Source: McGraw-Hill Professional
Earth Science Introductory Quiz The introductory test is 40 multiple-choice questions. While 40 questions can't cover every concept, skill, or shortcut taught in earth science, your performance on this test will give you a good indication of your strengths and ...
Introduction From the dawn of time, humans have looked up at the stars. Planets were once thought to be stars, but planets were special because they wandered across the sky, against the other fixed stars. The word planet, in fact, comes from the ancient ...
Introduction The soil we step on when we take a stroll in the woods is only a thin layer, sitting on top of rock that goes down mile after mile after mile – indeed thousands of miles, What is inside the earth? At the earth's core, temperatures are estimated ...
Introduction One of the most important discoveries of science in the last fifty years is that the Earth's continents move. Not only the continents, but the oceans move, too. In fact, oceans grow and shrink over tens to hundreds of millions of years. How this all ...
Introduction The key to the workings of earthquakes, volcanoes, and mountains is the theory of plate tectonics. Most of the action occurs at the edges of plates, the margins at which they slide, bump, and collide. What causes earthquakes and volcanoes? How are ...
Introduction The dynamic earth churns new matter up to its surface and returns other matter back down to the mantle. Through all this activity, including through the actions of water and wind as well as deposition of sediments to form new types of rock, continents ...
Introduction The earth, as we've seen, is about four and a half billion years old. Some rocks exist for all ages, except for the very oldest times. The geological cycles have created and destroyed mountains and even continents during the saga of plate tectonics, ...
Introduction From ancient times, people knew that air was crucial to life. But they did not know that air, which seems to be a single substance, is actually a mixture of many different gases. We will examine the contents of air later in this lesson. But first, we ...