volcanoes and vents
The most obvious landforms created by lava are volcanoes, most commonly as cinder cones, composite volcanoes, and shield volcanoes. Eruptions also take place through other types of vents, commonly from fissures (Figure 1.1). The eruptions that created the entire ocean floor are essentially fissure eruptions.
Viscous lava flows slowly. If there is not enough magma or enough pressure to create an explosive eruption, the magma may form a lava dome. Because it is so thick, the lava does not flow far from the vent. (Figure 1.2). Lava flows often make mounds right in the middle of craters at the top of volcanoes, as seen in the Figure 1.3. A fissure eruption on Mauna Loa in Hawaii travels toward Mauna Kea on the Big Is- land. Lava domes are large, round landforms created by thick lava that does not travel far from the vent. Lava domes may form in the crater of composite volcanoes as at Mount St. He- lens.
Lava creates new land as it solidifies on the coast or emerges from beneath the water (Figure 1.5). Lava flowing into the sea creates new land in Hawaii. Over time the eruptions can create whole islands. The Hawaiian Islands are formed from shield volcano eruptions that have grown over the last 5 million years (Figure 1.6). The island of Hawaii was created by hotspot volcanism. You can see some of the volcanoes (both active and extinct) in this mosaic of false-color composite satellite images.
A lava plateau forms when large amounts of fluid lava flow over an extensive area (Figure 1.4). When the lava solidifies, it creates a large, flat surface of igneous rock. Layer upon layer of basalt have created the Columbia Plateau, which covers more than 161,000 square kilometers (63,000 square miles) in Washington, Oregon, and Idaho.
landforms from magma
Magma intrusions can create landforms. Shiprock in New Mexico is the neck of an old volcano that has eroded away (Figure 1.7). The volcanic neck is the remnant of the conduit the magma traveled up to feed an eruption. The aptly named Shiprock in New Mexico.
landforms from lava
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fissure eruptions are rare in volcanic regions.
a) true --> b) false
mauna loa in hawaii is this type of volcano.
a) cinder cone volcano b) composite volcano --> c) shield volcano d) none of the above
large, round landforms created by thick lava that does not travel far from the vent:
--> a) lava dome b) lava volcano c) lava plateau d) lava neck
all of the volcanoes on the island of hawaii are about the same age.
a) true --> b) false
large amounts of fluid lava flow that solidifies and creates a large, flat surfaces of rock.
a) lava dome b) lava volcano --> c) lava plateau d) lava neck
lava plateaus are made from
--> a) layers of fluid lava. b) batholiths from down deep. c) overlying ash flows. d) alternating fluid lava and ash flows.
shiprock in new mexico is this type of landform.
a) volcanic dome --> b) volcanic neck c) volcano d) volcanic plateau
what type of rock created the columbia plateau?
a) quartz --> b) basalt c) granite d) slate
a volcanic neck is made by this part of a volcano.
a) crater b) pipe c) magma chamber --> d) vent
the hawaiian islands exist because
--> a) lava flows into the sea to create new land. b) ash flow eruptions extend land outward. c) plates smash together to create islands. d) magma chambers are uplifted so that they are above sea level.
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