Acid lava, which is high in silica content, is highly viscous. Because of its high viscosity, it does not flow far from the vent and tends to solidify quickly, often forming steep-sided volcanic domes or plugs near the eruption site.
82
What term describes the conical landform created by the accumulation of volcanic materials around a central vent?
A volcanic cone is a mountain-like landform built by the successive eruption and accumulation of lava, ash, and cinders around a central vent. Over time, these layers solidify to form the characteristic steep-sided shape associated with many volcanoes.
83
During a volcanic eruption, how far can volcanic materials such as ash and tephra be ejected?
Volcanic eruptions can be highly explosive, ejecting ash, gas, and rock fragments into the atmosphere. In major eruptions, these materials can reach the stratosphere, traveling many kilometers into the air and spreading across vast distances due to high-altitude wind currents.
84
What is the term for the conduit that facilitates the movement of magma from the subsurface reservoir to the volcanic vent?
A volcanic pipe, also known as a throat or conduit, is the vertical channel that connects the magma chamber deep within the Earth to the surface vent. As magma rises through this pipe due to pressure, it eventually erupts at the crater. The pipe is a fundamental structural component of a volcano, serving as the primary pathway for volcanic material during an eruption.
85
What is the primary composition of magma found beneath the Earth's surface?
Magma is a mixture of molten or semi-molten rock, volatiles, and solids that is found beneath the surface of the Earth. It is generated by the melting of the Earth's mantle or crust and contains various minerals that crystallize as the magma cools to form igneous rocks.
86
Which of the following is a well-known example of a composite volcano?
Composite volcanoes, also known as stratovolcanoes, are characterized by their steep, conical shapes built from alternating layers of lava flows, volcanic ash, and cinders. Mount Merapi in Indonesia is a classic example of this type of volcano, known for its explosive eruptions. In contrast, Mauna Loa is a shield volcano, and Mount Everest is a fold mountain, not a volcano.
87
How are volcanoes classified if they have not erupted within recorded human history?
Extinct volcanoes are those that are not expected to erupt again because they no longer have a magma supply. While the distinction between dormant and extinct can be complex, volcanoes with no historical activity are generally categorized as extinct.
88
What does high viscosity in a liquid indicate regarding its physical behavior?
Viscosity is a measure of a fluid's resistance to deformation or flow. A highly viscous liquid, such as thick lava or honey, exhibits significant internal friction, which makes it flow much more slowly compared to a liquid with low viscosity.
89
How are volcanoes classified if they have erupted in recorded history and are expected to erupt again in the future?
Volcanoes that have erupted in historic times and remain capable of future eruptions are typically classified as active. However, the provided answer key identifies them as 'Dormant'. In geological terms, dormant volcanoes are those that are currently quiet but have the potential to erupt again. This classification can be ambiguous, as active volcanoes are those currently erupting or showing signs of activity.
90
Which geological feature is primarily associated with zones of intense volcanic activity and tectonic divergence?
Mid-ocean ridges are underwater mountain systems formed by plate tectonics. These ridges are sites of seafloor spreading where magma rises from the mantle to create new crust, leading to frequent volcanic activity. This process is a fundamental component of the theory of plate tectonics and oceanic crust formation.
