The political events of the 1990âs have had significant effects on the number of Member. States of the United Nations. In 1990, the entry of both Namibia and Liechtenstein made the. number of members rise to 160; however the successive union of North and South Yemen, and.
Several types of volcanic eruptions âduring which lava, tephra (ash, lapilli, volcanic bombs and blocks), and assorted gases are expelled from a volcanic vent or fissure âhave been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed.here are two types of eruptions in terms of activity, explosive eruptions and effusive eruptions. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra. Effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption.
One of the two most important types of volcanoes, shield volcanoes are large and broad and have relatively gentle slopes. Kilauea on the island of Hawaii is good example of a shield volcano.Eruptions on shield volcanoes are far less explosive than those on composite volcanoes.That is because the basalt lava that erupts from shield volcanoes contains less silica, SiO 2, and is therefore less sticky (less viscous) and doesn't plug up the volcano. shield volcano is a type of volcano usually built almost entirely of fluid magma flows. They are named for their large size and low profile, resembling a warrior's shield lying on the ground.