Rocks and Earth Sciences

Which one of the following sedimentary rocks has not been formed mechanically?

[amp_mcq option1=”Sandstone” option2=”Conglomerate” option3=”Loess” option4=”Geyserites” correct=”option4″]

Geyserites, also known as siliceous sinter, are deposits formed by the precipitation of silica from hot springs and geysers. This is a chemical process, not a mechanical one.

Sedimentary rocks are classified based on their formation process. Mechanically formed (clastic) sedimentary rocks are composed of fragments of pre-existing rocks and minerals transported and deposited by agents like water, wind, or ice.

Sandstone is a clastic sedimentary rock formed from sand-sized grains. Conglomerate is a clastic sedimentary rock composed of rounded pebbles and cobbles. Loess is a clastic sediment composed of wind-blown silt-sized particles. These are all formed through mechanical processes of weathering, erosion, transport, and deposition of clastic material.

An avalanche is a type of which one of the following disasters ?

[amp_mcq option1=”Atmospheric” option2=”Terrestrial” option3=”Aquatic” option4=”Biological” correct=”option2″]

An avalanche is the rapid movement of a large mass of snow, ice, rock, or debris down a mountainside or slope. This is a geological phenomenon occurring on the land surface.

Disasters are often classified based on their origin or the sphere of Earth they primarily affect. Terrestrial disasters are those originating from the solid Earth or landforms.

Examples of terrestrial disasters include earthquakes, volcanic eruptions, landslides, and avalanches. Atmospheric disasters relate to weather and climate (e.g., cyclones, droughts, floods, heatwaves). Aquatic disasters relate to water bodies (e.g., tsunamis, limnic eruptions). Biological disasters involve living organisms (e.g., pandemics, epidemics, pest infestations).

Which one of the following is not a major tectonic plate?

[amp_mcq option1=”Saudi Arabian plate” option2=”Antarctica and the surrounding oceanic plate” option3=”India-Australia-New Zealand plate” option4=”Pacific plate” correct=”option1″]

The Earth’s lithosphere is divided into several large and small tectonic plates. Major plates are generally considered the largest ones. The seven widely recognized major plates are: Pacific, North American, Eurasian, African, Antarctic, Indo-Australian (or Australian and Indian), and South American. The Saudi Arabian plate is considered a minor plate that is separating from the African plate.

– There are generally considered to be seven major tectonic plates.
– The options B, C, and D (Antarctic, India-Australia-New Zealand/Indo-Australian, Pacific) are all classified as major plates.
– The Saudi Arabian plate is classified as a minor plate.

Besides the seven major plates, there are numerous minor plates (e.g., Arabian, Caribbean, Nazca, Scotia, Philippine Sea) and microplates. Plate tectonics is the theory explaining the movement of these plates and the resulting geological activity.

Which one of the following is not related to wind erosion?

[amp_mcq option1=”Wind gap” option2=”Zeugen” option3=”Dreikanter” option4=”Demoiselle” correct=”option1″]

Wind gap is not related to wind erosion.

– A wind gap is a pass through a ridge or mountain range from which a stream that formerly occupied it has been diverted, often by stream capture. It is a feature formed by fluvial erosion and capture, not wind erosion.
– Zeugen are mushroom-shaped rock formations resulting from differential wind erosion (abrasion).
– Dreikanter are ventifacts, rocks shaped and polished by wind abrasion, typically with three facets.
– Demoiselles (also called earth pillars or hoodoos) are rock pillars with a caprock, primarily formed by differential erosion by water (rain), though wind can play a secondary role. However, wind gap is distinctly not a wind erosion landform.

Wind erosion creates distinctive landforms primarily through deflation (removal of loose particles) and abrasion (grinding of rock surfaces by wind-borne particles). Landforms like yardangs, ventifacts, deflation hollows, and sand dunes are results of wind erosion and deposition.

Geomorphic factors influencing plant and animal distributions are

[amp_mcq option1=”slope angle and relief only” option2=”slope aspect and relative relief” option3=”slope angle, slope aspect and relief” option4=”slope angle, slope aspect and relative relief” correct=”option3″]

The correct answer is D) slope angle, slope aspect and relative relief.

Geomorphic factors relate to the physical characteristics of the Earth’s surface. Slope angle influences water runoff, soil erosion, and sun exposure. Slope aspect (the direction a slope faces) significantly affects the amount of insolation received, which impacts temperature and moisture levels. Relief refers to the variation in elevation within a given area; relative relief focuses on local differences in elevation. All these factors influence local climate conditions (microclimate), soil development, and drainage patterns, which in turn affect the types and distribution of plant and animal life. Options A, B, and C are incomplete as they do not list all the key geomorphic factors mentioned that are relevant to plant and animal distributions.

Other geomorphic factors that can influence species distribution include altitude (part of relief), terrain ruggedness, drainage patterns, and the presence of specific landforms like valleys, ridges, or plateaus. These factors interact with climatic and edaphic (soil) factors to create diverse habitats.

Statement I:
Portions of glacial troughs may exhibit remarkably flat floors.
Statement II:
The flat floor in a glacial trough is produced by uniform glacial erosion.

[amp_mcq option1=”Both the statements are individually true and Statement II is the correct explanation of Statement I” option2=”Both the statements are individually true but Statement II is not the correct explanation of Statement I” option3=”Statement I is true but Statement II is false” option4=”Statement I is false but Statement II is true” correct=”option3″]

Statement I is true; portions of glacial troughs (U-shaped valleys formed by glaciers) often have remarkably flat floors. Statement II is false. While glacial erosion (abrasion and plucking) is responsible for carving the overall U-shape and lowering the valley floor, the characteristic flatness is often achieved not solely by “uniform glacial erosion” (which is rarely truly uniform), but significantly by the deposition of glacial till (ground moraine) and outwash sediments after the ice retreats, filling irregularities on the eroded bedrock floor. Attributing the flatness purely to uniform erosion is inaccurate.

Glacial troughs are characterized by their U-shape, steep sides, and broad, often flat floor. The U-shape is formed by the powerful erosive action of the glacier flowing through a pre-glacial valley.

Processes contributing to the shape and features of a glacial trough include abrasion (grinding action of ice and embedded debris), plucking (lifting and removal of rock fragments), and basal melting. The deposition of ground moraine and later sediments like lacustrine deposits (in lakes formed after deglaciation) plays a crucial role in creating the final flat appearance of the valley floor.

Statement I:
By far the most common topographic form in a Karst terrain is the sinkhole.
Statement II:
Topographically, a sinkhole is a depression that varies in depth from less than a meter to few hundred meters.

[amp_mcq option1=”Both the statements are individually true and Statement II is the correct explanation of Statement I” option2=”Both the statements are individually true but Statement II is not the correct explanation of Statement I” option3=”Statement I is true but Statement II is false” option4=”Statement I is false but Statement II is true” correct=”option1″]

Statement I is true as sinkholes are indeed the most common and characteristic topographic features in Karst landscapes, formed by the dissolution of soluble bedrock. Statement II is also true; sinkholes vary significantly in size and depth, from shallow depressions to large collapsed features. However, Statement II describes a characteristic of sinkholes (their varying depth) and not the reason why they are the *most common* form. The commonality arises from the widespread nature of the dissolution process in soluble rocks. Therefore, Statement II is not the correct explanation for Statement I.

Karst topography is formed by the dissolution of soluble rocks like limestone, gypsum, and dolomite. Sinkholes are depressions formed by this dissolution and are a defining feature of Karst. Sinkholes can form through solutional processes at the surface or collapse of overlying material into underlying cavities.

Other features common in Karst terrains include caves, underground drainage systems, disappearing streams, dolines, uvalas, and poljes. The size and shape of sinkholes depend on the depth of the water table, thickness of the overlying soil, and the specific rock structure.

Stalactites and stalagmites are features of:

[amp_mcq option1=”glacial topography” option2=”volcanic topography” option3=”karst topography” option4=”fluvial topography” correct=”option3″]

Stalactites and stalagmites are depositional landforms found in caves formed in soluble rocks, typically limestone. These features are created by the precipitation of calcium carbonate from dripping water. Such landscapes characterized by the dissolution of soluble rocks are known as karst topography. Stalactites hang from the cave ceiling, while stalagmites rise from the cave floor.

Stalactites and stalagmites are characteristic features of karst topography, which develops in areas with soluble rocks like limestone, dolomite, or gypsum.

Glacial topography includes features like moraines, cirques, and U-shaped valleys formed by glacial erosion and deposition. Volcanic topography includes features like volcanoes, lava flows, and calderas formed by volcanic activity. Fluvial topography includes features like river valleys, meanders, and deltas formed by river processes.