Static Quiz 19 February 2024 (Geography)

Solution: C
Justification: Metamorphic rocks are made by either heating up or squashing the earth’s crust. They are often found in mountainous regions. One example is slate. Slate was originally a black mud laid down on the bottom of the sea or lake. Fossils can sometimes be found in it but they are often squashed. Other common metamorphic rocks are called marble, gneiss, schist. Earth movements can cause rocks to be deeply buried or squeezed. As a result, the rocks are heated and put under great pressure. They do not melt, but the minerals they contain are changed chemically, forming metamorphic rocks. Sometimes, metamorphic rocks are formed when rocks are close to some molten magma, and so get heated up. When a metamorphic rock is formed under pressure, its crystals become arranged in layers.

Solution: A
Justification: The streams within a drainage basin form various patterns depending on the slope of land, underlying rock structure as well as the climatic conditions of the area. These are dendritic, trellis, rectangular, and radial patterns. The dendritic pattern develops where the river channel follows the slope of the terrain. The stream with its tributaries resembles the branches of a tree, thus the name dendritic. A river joined by its tributaries, at approximately right angles, develops a trellis pattern. A trellis drainage pattern develops where hard and soft rocks exist parallel to each other. A rectangular drainage pattern develops on a strongly jointed rocky terrain. The radial pattern develops when streams flow in different directions from a central peak or dome like structure.

Solution:A
Justification: Gneiss usually forms by regional metamorphism at convergent plate boundaries. It is a highgrade metamorphic rock in which mineral grains recrystallized under intense heat and pressure associated with mountain building and volcanic activity. This alteration increases the size of the mineral grains and segregated them into bands, a transformation which made the rock and its minerals more stable in their metamorphic environment. Gneiss can form in several different ways. The most common path begins with shale, which is a sedimentary rock. Regional metamorphism can transform shale into slate, then phyllite, then schist, and finally into gneiss.

Solution: D
Justification: Block and Granular Disintegration type of weathering is carried out in deserts by rapid changes of temperature, or in mountains through frost action. Desert regions experience a large diurnal range of temperature due to direct heating by the sun during the day and rapid radiation at night. The rocks successively expand and contract. The repeated expansion and contraction of the rocks tends to enlarge joints and large rock masses ultimately break into angular blocks. This process is called block disintegration. Rocks having vertical joints are more susceptible to this form of weathering. The rocks having curvilinear joints get weathered. If water seeps in the cracks of the rocks, it exerts further pressure from inwards resulting in cracking of the rock.

Solution: C
Justification: Magma cools slowly as it rises towards Earth’s surface. It can take thousands to millions of years to become solid when it is trapped inside Earth. As the magma cools, solid rocks form (igneous). These rocks are mixtures of minerals. Granite is a common rock that forms when magma cools. Granite contains the minerals quartz, plagioclase feldspar, and potassium feldspar. The same igneous rock can be eroded, weathered, transported, deposited and consolidated as sedimentary rocks which are the source of nonmetallic minerals.