Q:

How is gabbro formed?

A:

Quick Answer

Gabbro, a type of intrusive igneous rock, is formed when magma cools and solidifies inside the crust of the Earth. Because it cools slowly, it is coarsely grained.

Know More

Full Answer

Gabbro is the intrusive equivalent to basalt, an extrusive rock formed by molten magma that cools on the Earth's surface. However, unlike extrusive rocks, which cool rapidly when exposed to the atmosphere, intrusive rocks, surrounded by pre-existing rock, push up from within the Earth and cool in a process that can take millions of years. Large deposits of gabbro lie beneath the oceanic crust, where magma cools extremely slowly to form large-grained holocrystalline masses. Gabbro is found in many places on Earth. It is also present on the moon.

The German geologist Christian Leopold von Buch, who studied the volcanic origins of minerals in Italy, named gabbro after a town in Tuscany. Gabbro is dense and dark-colored. Unlike granite, it contains no quartz and little silica. It contains pyroxene, plagioclase, amphibole and olivine. It often contains large but low-grade amounts of gold, silver, platinum, chromium, nickel and cobalt. Its dark appearance precludes its widespread use in construction, but it is often used for paving stones, headstones for graves and kitchen countertops, in which case it is referred to erroneously as "black granite."

Learn more about Geology

Related Questions

  • Q:

    How is natural gas formed?

    A:

    There are a couple of theories regarding how natural gas may have been formed in the Earth. One theory stipulates that natural gas was formed when prehistoric animals and plants were buried under deep layers of Earth. Another theory states that the Earth's natural gas was created even earlier, when the Earth was first formed more than 4.5 billion years ago.

    Full Answer >
    Filed Under:
  • Q:

    How is an archipelago formed?

    A:

    Archipelagos form when underwater volcanoes continually produce molten magma that cools and builds up to eventually form a group of islands. Although archipelagos can form by erosion or by the movement or evaporation of water, volcanic activity is the most common cause of archipelago formation.

    Full Answer >
    Filed Under:
  • Q:

    What causes magma to rise to Earth's surface?

    A:

    Magma rises to the surface because it is less dense than the surrounding rocks and a structural zone in the Earth's crust enables movement. When it reaches the surface, magma is referred to as lava. Magma may collect under the surface in an area called a magma chamber until it cools and forms igneous rock, or it may escape through the surface in a volcanic eruption.

    Full Answer >
    Filed Under:
  • Q:

    What is meant by uplift in geology?

    A:

    In geology, uplift refers to a considerable vertical movement of the Earth's crust and is one of the primary factors in the formation of mountains and other prominent landscape features. Some of the more spectacular examples of uplifts in the Earth's crust are the results of tectonic plate interactions that are involved in the process called orogenesis. Major mountain ranges, such as the Alps, were produced by the orogenic uplift resulting from a collision of one continental plate with another.

    Full Answer >
    Filed Under:

Explore