Basalt Rocks

Introduction
Basalt rocks are the most common dark-colored igneous rocks you will find. They contain ferrogmanesian minerals which are iron and magnesium rich. The shield volcanoes of Hawaii, cinder cones in the Pacific Northwest and the floors of the world's oceans are made of basalt.

Pillow basalt, NOAA

Pillow basalt on the ocean floor, NOAA

Basalt
Basalt is a dark heavy lava that is very hot and fluid when it erupts. It it erupts on the continents it can flow many kilometers before it cools in thin layers.

Flood basalts
Flood basalts made up of thin layers of lava flows cover thousands of square miles in Oregon and Washington. The layers of lava are over three miles thick near Yakima, Washington. Layers of flood basalts are exposed in the scenic Columbia George that separates Washington and Oregon.

Cinder cones
Cinder cones are small cone shaped volcanoes created entirely of basalt rocks blown out of a volcano. The magma beneath the volcano vent contains large amount of molten rock and gas mixed together under pressure.

Cinders (scoria)
The cinders (scoria) are erupted during small explosive eruptions which creates steep-sided volcanoes. Most of the cinders on the volcano are about the size of a golf ball or walnut. Cinder cones are also called scoria cones by geologists in some areas. 

Lava Bombs
Lava bombs are larger pieces of lava that were partly molten during the eruption. These rocks take on aerodynamic shapes while they are airborne. In general all the rocks that form a cinder cone are called cinders no matter how large or small the rocks are that formed during an eruption.

More Rock Cycle Links

Salt Domes Learn more about how salt domes form, what they are used for and how they are sometimes a key to find oil.

Lava Caves Find out how pahoehoe lava flows form lava caves.

Ignimbrite Learn more about ignimbrite that forms during large volcanic eruptions that produce pyroclastic flows.

Coal Formation Find out how leaves falling into a swamp can turn into coal.


Pahoehoe-Lava Find out how pahoehoe lava forms in the Hawaiian Islands.

Basalt Rocks These rocks cover the floors of all the oceans, create cinder cones and form the largest volcanic mountains on Earth.

Rock Cycle Learn more about igneous, sedimentary and metamorphic rocks and how they form.

Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more.