GEOLOGY...
is the study of Rocks. Although geologists cannot actually see what is inside the Earth, their research shows that it consists of layers. This structure is shown below:
This YouTube Clip will help you understand more on the structure of Earth
The first rocks
The first rocks of the crust and upper mantle formed long ago when material called magma cooled and solidified. Magma is very hot molten (melted) rock.
Scientist think that magma forms within the lower mantle. Dissolved gases make magma less dense than surrounding rock and pushes it upwards through any fault or crack in the crust above. On the way, magma melts more rock from the upper mantle and crust. If the magma reaches the surface, it is known as Lava. Lava has a temperature of about 1200 Degrees Celsius when it erupts at the surface of the Earth. These eruptions form Volcanoes, one type of which is shown below:
Scientist think that magma forms within the lower mantle. Dissolved gases make magma less dense than surrounding rock and pushes it upwards through any fault or crack in the crust above. On the way, magma melts more rock from the upper mantle and crust. If the magma reaches the surface, it is known as Lava. Lava has a temperature of about 1200 Degrees Celsius when it erupts at the surface of the Earth. These eruptions form Volcanoes, one type of which is shown below:
IGneous Rocks
Igneous
Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes (in this case, it is called lava). When lava cools very quickly, no crystals form and the rock looks shiny and glass-like. Sometimes gas bubbles are trapped in the rock during the cooling process, leaving tiny holes and spaces in the rock.
Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes (in this case, it is called lava). When lava cools very quickly, no crystals form and the rock looks shiny and glass-like. Sometimes gas bubbles are trapped in the rock during the cooling process, leaving tiny holes and spaces in the rock.
Intrusive vs. Extrusive: Igneous rocks can be classified into two main categories: intrusive and extrusive. A trick to help you remember intrusive and extrusive is to think of intrusive -- inside and extrusive -- exit.
Intrusive rocks come from magma. They cool slowly deep in Earth's crust. When magma cools underground, the crust acts like a blanket, insulating it, keeping it warm longer. Because the magma cools slowly, crystals of different minerals have time to grow. The molecules in the magma have time to arrange themselves into crystal formations before the magma hardens. Intrusive rocks have large crystals that can be seen with the naked eye. A common example of an intrusive igneous rock is granite.
Extrusive igneous rocks come from lava. Lava, at the surface, is exposed to air and water which causes the molten rock to cool rapidly. Solidifying rocks at the surface cool too quickly for large crystals to form. Molecules in the lava do not have time to arrange themselves to form large crystals. Extrusive rocks have crystals that are too small to see without magnification. A common example of an extrusive igneous rock is basalt. Some extrusive rocks, such as obsidian and pumice, cool so rapidly that they completely lack crystal structure and are considered a volcanic glass. Pumice is just like obsidian except it is tiny shards of glass.
Intrusive rocks come from magma. They cool slowly deep in Earth's crust. When magma cools underground, the crust acts like a blanket, insulating it, keeping it warm longer. Because the magma cools slowly, crystals of different minerals have time to grow. The molecules in the magma have time to arrange themselves into crystal formations before the magma hardens. Intrusive rocks have large crystals that can be seen with the naked eye. A common example of an intrusive igneous rock is granite.
Extrusive igneous rocks come from lava. Lava, at the surface, is exposed to air and water which causes the molten rock to cool rapidly. Solidifying rocks at the surface cool too quickly for large crystals to form. Molecules in the lava do not have time to arrange themselves to form large crystals. Extrusive rocks have crystals that are too small to see without magnification. A common example of an extrusive igneous rock is basalt. Some extrusive rocks, such as obsidian and pumice, cool so rapidly that they completely lack crystal structure and are considered a volcanic glass. Pumice is just like obsidian except it is tiny shards of glass.
Chapter 8.1: quizlet
UNIT REVIEW
Complete the following questions from your textbook on page 285:
Remembering: Q1- 5
Understanding: Q6- 9
Applying: Q10
Analysing: Q14, 15
Evaluating: Q17
Remembering: Q1- 5
Understanding: Q6- 9
Applying: Q10
Analysing: Q14, 15
Evaluating: Q17