Laryngomalacia is the most common cause of chronic stridor in children younger than two years. It has a male-to-female ratio of approximately 2:1.1 The condition is due to an intrinsic defect or delayed maturation of supporting structures of the larynx.
Volcano Rocks Igneous Rocks. Introduction Volcano rocks are igneous rocks that form during a volcanic eruption. They were all once magma which is molten rock beneath the Earth's surface. There are four major groups of the igneous rocks: basalt, andesite, dacite and rhyolite. Each of these different rock groups form different types of volcanoes. Volcanic rocks forming during eruption of Kilauea, USGS Rhyolite rocks Rhyolite magma cooling underground forms granite.
Back to Encyclopedia. Basalt is the most common volcanic rock: It is formed as the volcanic magma erupts onto the surface or even in the water and undergoes a rapid cooling process.It has varying shades of grey to black. The fast cooling process makes the creation of the minerals almost invisible, making it a fine-grained substance.ack to Encyclopedia. Basalt is the most common volcanic rock: It is formed as the volcanic magma erupts onto the surface or even in the water and undergoes a rapid cooling process.