How does igneous rock turn into magma

Hypabyssal rock is a form of intrusive igneous rock that solidifies at medium to shallow depths within the crust, usually in fissures as dikes and intrusive sills. These rocks typically have an intermediate grain size and texture between that of intrusive and extrusive rock. As might be expected, they show structures that intermediate between those of extrusive and plutonic rocks.

Common examples of subvolcanic rocks are diabase, quartz-dolerite, micro-granite and diorite. Igneous rocks are classified according to their mode of occurrence, texture, mineralogy, chemical composition, and the geometry of the igneous body.

Two important variables that are used for the classification of igneous rocks are particle size and the mineral composition of the rock. Feldspar, quartz, olivines, micas, etc.

Types of igneous rocks with other essential minerals are very rare. In simplified classification, igneous rocks are separated by the type of feldspar present, the presence or absence of quartz, and — in cases where feldspar or quartz are not present — by the type of iron or magnesium minerals present.

Rocks containing quartz are silica-oversaturated, while rocks with feldspathoids are silica-undersaturated. Igneous rocks which have crystals large enough to be seen with the unaided eye are classified as phaneritic, while those with crystals too small to be seen are aphanitic.

Typically, rocks belonging to the phaneritic class are intrusive in origin, while aphanitic rocks are extrusive. In the first few lectures I mentioned that certain isotopes of certain elements were unstable and underwent radioactive decay.

Think about a pan of pop corn on the stove. Each kernel has the potential to pop, but they do it one at a time. You never know which particular kernel is going to pop, but you know if you wait long enough, most of them will have popped. All else being equal i. As the number of kernels dwindles, the number of popped corn kernels increases. You could plot the number of kernels left to be popped and the number that have already popped :.

The time scale is determined by the half-life or the time it takes for half the kernels to pop. From looking at the graph, it is obvious that the number remaining at any time decreases with time, and more pop per unit time than pop later, when there are fewer left to pop.

In fact, the number that pop during any interval depends on the number of unpopped kernels that were there at the beginning of the interval. The special number is called "e" and is about 2. The time constant is some number that depends on the rate at which the pop corn pops. I used the number the natural log of 2 0. Join our community of educators and receive the latest information on National Geographic's resources for you and your students.

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Related Resources. View Collection. View Article. Rocks, rocks, rocks. Weathering is all about rocks. To understand weathering, we must first learn about rocks. Rocks are the most common of all materials on earth. They are familiar to everyone. You may recognize rocks in the form of a mountain near your hometown, the gravel in a driveway, the cliffs lining your favorite fishing hole, or the granite or sandstone or limestone your fingers and toes cling to at your favorite climbing area.

Rocks should be considered products of their environment - when their environment changes, so will the ways the rock weathers and erodes, or is otherwise shaped. Rocks form in one of two distinct environments: either below the surface of the earth or at its surface.

Rocks are composed of minerals. Minerals are naturally occurring, inorganic substances, which have an ordered internal structure giving them a specific appearance. Interestingly, ice is a mineral. Some of the more common rock-forming minerals are quartz, feldspar, pyroxene, hornblende, and olivine. Minerals should not be confused with rocks.

For example, granite is a rock. The triad don't you love that word, triad? You can learn about rock types and other things in great detail below. But here's the real important stuff about rocks and rock types that are integral to understanding this module:. There are three rock types - there are a lot of sedimentary; some granite; and very little metamorphic rocks on the Colorado Plateau The rock cycle happens - how rocks form determines how they will weather Rocks weather differentially - without differential weathering, the landscape would not be as strikingly diverse!

In this Module, you will encounter a LOT of sandstone. Sandstone is a sedimentary rock that is highly resistant to weathering. Other sedimentary rocks you will encounter are mudstone and siltstone. These are soft and easily weathered lots in the Painted Desert. Yet another sedimentary rock you will see is limestone. Limestone is composed of calcium carbonate, which is water soluble it dissolves in water. Therefore, the limestone you find in a dry area will remain a rock a lot longer than limestone you find in a MOIST area.

Regarding metamorphic rocks, there really aren't many of these on the Colorado Plateau.. So, good thing for you, we are really not going to cover this rock type in this Module.

You will see a few igneous rocks in this Module You see granite intrusive igneous and basalt extrusive igneous.

The granite you will see is high up in the La Sal Mountains and the basalt you will see sits as cap rocks on top of softer, underlying sediments. A cap rock is a comparatively more resistant rock that protects the rocks beneath it from weathering and eroding. The key to understanding rock weathering is to realize that rocks weather at different rates and into different forms based on their chemical composition and based on what weathering processes dominate the area.

For WAY more information on rocks than you are required to know for this Module, visit the following links:. Jump to igneous Jump to metamorphic Jump to sedimentary. Weathering breaking down rock and erosion transporting rock material at or near the earth's surface breaks down rocks into small and smaller pieces.

These smaller pieces of rock such as sand, silt, or mud can be deposited as sediments that, after hardening, or lithifying, become sedimentary rocks. Extreme pressure from burial, increasing temperature at depth, and a lot of time, can alter any rock type to form a metamorphic rock.

If the newly formed metamorphic rock continues to heat, it can eventually melt and become molten magma. When the molten rock cools it forms an igneous rock. Metamorphic rocks can form from either sedimentary or igneous rocks.

The sedimentary particles from which a sedimentary rock is formed can be derived from a metamorphic, an igneous, or another sedimentary rock. All three rock types can be melted to form a magma. Thus, the cycle has continued over the ages, constantly forming new rocks, breaking those down in various ways, and forming still younger rocks.

Rocks at the surface of the earth range in age from over three billion years old to a few hundred years old. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Igneous rock forms when magma cools and makes crystals.

Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool. Igneous rock can form underground, where the magma cools slowly.