Geologic Features And Events

Question 1

Geologic Features and Events

Folds, Faults, and Joints

Answer 1

● Tectonic movements create tremendous forces that cause the deformation of rock layers. Deformation of rocks may form folds, faults, and joints.

● A fold is a bend in the rock resulting from the compression of rock layers when continents collide. This process forms folded mountain ranges like the Himalayas. The upfold is the anticline while the downfold is the syncline. This is what happened to rocks when they are compressed.

Question 2

Geologic Features and Events

Folds, Faults, and Joints

Answer 2

● A fault is a fracture along the rocks that forms when rock layers break and move along the surface resulting to rock displacement. Fault block mountain ranges are formed through this process. Some faults are a single structure in rocks but most are numerous and closely spaced fractures within the fault zone.

● Just like a fault, a joint is also a fracture in the rock except that the rocks on either side have not moved. Most rocks near the earth’s surface are jointed rocks.

Question 3

Geologic Features and Events

Subduction zones

Answer 3

● The sinking of a subduction plate forms a long narrow depression known as trench. A plate may go under another plate and sink into the asthenosphere along a subduction zone. Subduction zones are located along continental margins.

● When a sinking plate goes into the asthenosphere, a large quantity goes into the asthenosphere, a large quantity of magma is produced by a process that gives rise to volcanoes along a subduction zones.

● Plates that sink in subduction zones are turned into magma.

Question 4

Geologic Features and Events

Rift Valleys and Ocean Ridges

an extremely long depression that develops along divergent plates.

formed because the continental crust stretches, fractures, and sinks as it is pulled apart
along divergent plates.

Answer 4

rift valley

Question 5

Geologic Features and Events

Rift Valleys and Ocean Ridges

are submarine mountain ranges that are formed when magma goes into the ocean floor.

The new lithosphere at the spreading center is hot and of low density.

Therefore, it floats to a higher level forming underwater mountain chains called mid-ocean ridges.

Answer 5

Ocean ridges

Question 6

takes place in three tectonic environments:

✔ the spreading center

✔ mantle plumes

✔ subduction zones

Answer 6

Magma intrusion

Question 7

● Magma along the spreading centers erupts from the ridge beneath the sea and solidifies to form a new oceanic crust. The oceanic crust spreads outward as it lies on top of the separating tectonic plates. Because mantle plumes and hot spots form below the lithosphere, hot spots can occur within the tectonic plate.

● If mantle plumes rise beneath the sea, volcanic eruptions build submarine volcanoes and volcanic islands. Along subduction zones, volcanoes and plutonic rocks are common features.

Question 8

are generated along faults due to the breaking or movement of rock layers. During
earthquakes, rocks move from a few centimeters up to about two meters.

Answer 8

Earthquakes

Question 9

There are geologic activities that do not occur along plate boundaries. Some activities take place within a tectonic plate.

caused by a mantle plume.

Answer 9

intraplate activities

Question 10

a small rising column of hot plastic mantle rock. As the mantle rock goes near the
surface, pressure that causes it to melt and form a hot spot is released. Eruption of this hot spot gives rise
to volcanoes.

Answer 10

mantle plume