What is the difference between lava and igneous rock

Once the lava has erupted, it cools and solidifies into rock:. It is a heavy, dark, grainy rock. When it comes out of the volcano, it is hot and liquid.

The Auckland volcanic field has erupted this type of hot, runny iron-rich lava, and the landscape is dotted with mountains made from basalt and scoria a red-coloured rock that contains large amounts of iron-rich minerals. Both rock types are excavated for building materials and landscaping. Some scoria rocks fall within the andesite classification because of their chemical composition. Some rhyolitic rocks are quite light, for example, pumice, which may still have evidence of the bubbles of gas trapped as the rock solidified.

In the activity, Identifying volcanic rocks students watch a video describing different types of volcanic rocks and then match the chemical composition and type of volcanic eruption each rock is associated with. Can we predict earthquakes? Why does a building on solid bedrock resist better to an earthquake than a building on sediment or reclaimed land? Why does a building with base isolation resist better to an earthquake than a building without base isolation?

Why does a building with full bracing resist better to an earthquake than a building with no bracing? Impacts of Volcanic Hazards What are the principal signals of a volcanic unrest? How can we forecast volcanic eruptions? Tsunamis Where is a tsunami most likely to happen? Can Singapore be affected by a tsunami? Can animals sense an impending tsunami?

What should we do during a tsunami? Why do trees seem to resist more to tsunamis than houses? Why does a boat at sea experience a tsunami differently from a boat near the shore? Volcanoes All About Volcanoes What is the difference between magma and lava? Is lava always liquid? This is a vertical columnar basalt formation. When basaltic lava cools it often forms hexagonal six sided columns. Pumice is a very light colored, frothy volcanic rock.

Pumice is formed from lava that is full of gas. The lava is ejected and shot through the air during an eruption. As the lava hurtles through the air it cools and the gases escape leaving the rock full of holes. Pumice is so light that it actually floats on water.

Huge pumice blocks have been seen floating on the ocean after large eruptions. Some lava blocks are large enough to carry small animals. Pumice is ground up and used today in soaps, abrasive cleansers, and also in polishes. Rhyolite is very closely related to granite.

The difference is rhyolite has much finer crystals. These crystals are so small that they can not be seen by the naked eye. Rhyolite is an extrusive igneous rock having cooled much more rapidly than granite giving it a glassy appearance. The minerals that make up rhyolite are quartz, feldspar, mica, and hornblende.

Gabbros are dark-colored, coarse-grained intrusive igneous rocks. They are very similar to basalts in their mineral composition. They are composed mostly of the mineral plagioclase feldspar with smaller amounts of pyroxene and olivine.

Obsidian is a very shiny natural volcanic glass. When obsidian breaks it fractures with a distinct conchoidal fracture. Notice in the photo to the left how it fractures. Intrusive rocks are formed from magma that cools and solidifies within the crust of the planet.

When lava comes out of a volcano and solidifies into extrusive igneous rock, also called volcanic, the rock cools very quickly. Crystals inside solid volcanic rocks are small because they do not have much time to form until the rock cools all the way, which stops the crystal growth. If lava cools almost instantly, the rocks that form are glassy with no individual crystals, like obsidian. There are many other kinds of extrusive igneous rocks. Intrusive rocks, also called plutonic rocks, cool slowly without ever reaching the surface.

They have large crystals that are usually visible without a microscope. This surface is known as a phaneritic texture. Perhaps the best-known phaneritic rock is granite. One extreme type of phaneritic rock is called pegmatite , found often in the U. Pegmatite can have a huge variety of crystal shapes and sizes, including some larger than a human hand. Rock texture with crystals that are invisible without magnification.