(63) Answer:

At the younger stage of a stream different size and shapes of hard rock particles are added to the flow due to rapid mechanical weathering action. These particles have sharp edges at the very beginning of its formation. However, intensive mechanical weathering action at the younger stage of a river causes to remove sharp and irregular edges of such partials mentioned above with the long distance of their travel in the flow path. This is mainly due to the action of mechanical erosion at the early stages of the river flow. Finally, mechanical weathering of the long distance transported particles cause to produce well rounded particles with smooth surfaces.

(62) Answer:

If we take the cross section of the meander, out side of the curve of meandering channel has a high flow velocity than its inner side curve and tend to produce turbulent flow at the outer side of the meander. Therefore at the outer side of the curve experience more erosion. Because the turbulent flow causes to erode the bank including the bottom of the stream, under the conditions of the mechanical weathering. By the way at the inner side of the meandering curve, sediments of the stream flow tend to settle at its bank. Due to such sediment deposits, further decrease of flow velocity will be taken place.

Answer for Q (61):

Type 1 - This diagram shows younger stage of the river flow. Because it tends to form “V” shaped valley with steep sides of its flow path. It is due to erosion of its bed more rapidly than it erodes its bank. Further it has almost straight flow path. It does not consist of deposition of sediments. These all are due to high velocity of river flow under the highest gradient condition than older and younger stages of a river flow.

Type 2 - It indicates older stage of a river flow. According to the diagram the river flows, forming very broad valley with flat plain. The broad flat plain formed mainly due to sedimentation process and erosion of valley walls of the river at its older stage.Additionally at this stage the river carryout large amount of sediments with its flow and it causes to decrease the stream flow velocity at this stage of flow. Further, river has significant meanders and tends to form oxbow lakes on its flow path. This is due to decrease of flow velocity under the lowest gradient conditions of the main river comparatively with other two stages (younger & mature) of the river flow.

According to the above explanation given under the Type 1 and Type 2, it can that the find difference of stream velocities with relate to different ages of stream formation. Therefore type 1 that the stream at younger stage, it has higher average flow velocity than the older age is represented by the type 3.

Answer:

X- 44.5^oN and 73.7^o W

This stream pattern can be identified as Trellis (or some time calls as

Espalier) according to the geological stream pattern categorization. This stream pattern has a network of parallel or sub parallel streams that is resulted due to strong structural events of geology such as tight regional folding. Tight regional folding followed by alteration of hard and weak formations of underline bedrock structure cause to form ridge and valley geomorphology similarly depicted in the diagram number 04. In such geomorphological condition, streams align themselves in the valleys parallel to ridges with minor tributaries coming almost at right angles through weathering of weak structurally control bedrock units

Important points to stress include:

There is another stream network system that named as Rectangular stream pattern which one can observe very similar to Trellis stream pattern. However, it is significant that the rectangular stream pattern tend to develop where the areas common with tectonic faults or bed rock joints. In this pattern, the tributary streams make more shape bends and enter the main stream at high angles than in Trellis stream pattern.

Based on these arguments, the rest of the options are incorrect

Correct Answer: South American Plate and the Nazca Plate (3)

The diagram illustrates that two plats are moving toward each other. When two plates move toward one another, they form either a subduction zone or a continental collision(convergent plate margin). This depends on the nature of the plates involved. In the above diagram one plate is composed of oceanic lithosphere and the other is composed of continental lithosphere, the denser oceanic plate is subducted, often forming an orogenic belt and associated mountain range. This type of convergent boundary is similar to the Andes. Andes mountain range is formed subduction of the Nazca Plate beneath the South American Plate forming the Peru-Chile trench.

All other plates boundaries represent divergent plate boundaries. At divergent boundaries, two plates move apart from each other and the space that this creates is filled with new crustal material sourced from molten magma that forms below.

Based on these arguments, the rest of the options are incorrect.

Correct Answer: Option 1 – Violet

The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 380 to 750 nm. Following diagram shows the different wavelengths and their frequency visible spectrum

From the visible spectrum violet has the lowest wavelength; that is 380-450 nm.

Based on these arguments, the rest of the options are incorrect

Correct answer: option (4) Cleavage

In above diagram, mineral shows sharp breakages along the crystal face. That is cleavages of the mineral.

Cleavage – Many minerals will, when broken will display a flat plane of breakage which is parallel to a possible crystal face. Cleavage planes are developed along planes of weakness in the atomic lattice and perfection or otherwise of the cleavage depends upon the relative strength of the bonds in this plane.

Important points to stress include:

Hardness - Hardness is the property of a mineral to resist abrasion. Some minerals can be scratched easily while others are almost impossible to scratch.

Fracture – The breakage of a mineral in a direction other than that of cleavages in

crystalline mineral and in any direction in other minerals.

Streak – Streak of a mineral is its colour in a finely divided state.

Based on these arguments, the rest of the options are incorrect.

Correct Answer: Option 4 – Very coarse texture

Igneous rocks are formed from the cooling of molten (melted) rocks. Igneous rocks may be extrusive on the earth’s surface or intrusive into the rocks forming the crust of the earth. The molten rock material below the earth is known as magma and when it comes to the earth surface is known as lava.

Pegmatite-

A very coarse-grained intrusive igneous rock having a grain size of 3cm or larger, with crystals occasionally reaching a meter or so in length; very rarely, lengths of some ten meters or so have been recorded.

Above diagram shows, very coarse grained texture. Normally very coarse grained textures are formed due to the slow cooling of magma. To cool very slowly, temperature gradient should be very low. That is difference between temperature of the magma and temperature of the surroundings is low. Magma has high temperature and to form large crystals (coarse grained texture) surrounding temperature should be that much of high. As the temperature below the earth surface is very high, molten rock materials cools slowly, taking ten’s of thousand of years to cool and formed very coarse grained Pegmatite.