Static Quiz 30 March 2022 (Geography)

Extrusive Volcanic Landforms:

Extrusive landforms are formed from material thrown out to the surface during volcanic activity.
The materials thrown out include lava flows, pyroclastic debris, volcanic bombs, ash, dust and gases such as nitrogen compounds, sulphur compounds and minor amounts of chlorine, hydrogen and argon.
Examples: Conical Vent and Fissure Vent
Mid-Ocean Ridges
Composite Type Volcanic Landforms
Shield Type Volcanic Landforms
Fissure Type Flood Basalt Landforms (Lava Plateaus)
Crater
Caldera
Cinder cone
Lava Dome

Mid oceanic ridges and Crater are examples of Intrusive Volcanic landforms.

Fluvial Erosional Landforms
• Fluvial Erosional Landforms are landforms created by the erosional activity of rivers.

Various aspects of fluvial erosive action include:
• Hydration: the force of running water wearing down rocks.
• Corrosion: chemical action that leads to weathering.
• Attrition: river load particles striking, colliding against each other and breaking down in the process.
• Corrasion or abrasion: solid river load striking against rocks and wearing them down.
• Downcutting (vertical erosion): the erosion of the base of a stream (downcutting leads to valley deepening).
• Lateral erosion: the erosion of the walls of a stream (leads to valley widening).
• Headward erosion: erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, and so causes the stream channel to lengthen.

The Crust
• The crust is the outermost solid part of the earth.
• It is fragile.
• The thickness of the crust varies under the oceanic and continental areas.
• Oceanic crust is thinner as compared to the continental crust.
• The continental crust is thicker in the areas of major mountain systems.

The Mantle
• The portion of the interior beyond the crust is called the mantle.
• It is in a solid-state.
• It has a density higher than the crust portion.
• The thickness ranges from 10-200 km.
• The mantle extends from Moho’s discontinuity to a depth of 2,900 km.
• The asthenosphere is the upper portion of Mantle.
• It is the chief source of magma that finds its way to the surface during volcanic eruptions.
• The crust and the uppermost part of the mantle are called the lithosphere.

The Core
• The core-mantle boundary is positioned at the depth of 2,900 km.
• The inner core is in the solid-state whereas the outer core is in the liquid state.
• The core is made up of very heavy material mostly constituted by nickel and iron. Hence it is also called the “nife” layer.

According to India Met Department (IMD), the Arabian Sea arm of south-west monsoon is counting on an itinerant Madden-Julian Oscillation (MJO) wave for normal monsoon.

It is an oceanic-atmospheric phenomenon which affects weather activities across the globe. It brings major fluctuation in tropical weather on weekly to monthly timescales. Hence statement 1 is correct.

The MJO can be defined as an eastward moving ‘pulse’ of clouds, rainfall, winds and pressure near the equator that typically recurs every 30 to 60 days. It’s a traversing phenomenon and is most prominent over the Indian and Pacific Oceans. Hence statement 2 is incorrect.

Phases of Madden-Julian Oscillation
• The MJO consists of two parts or phases. Strong MJO activity often dissects the planet into halves. One half within the enhanced convective phase and the other half in the suppressed convective phase.
• Enhanced rainfall (or convective) phase: winds at the surface converge, and the air is pushed up throughout the atmosphere. At the top of the atmosphere, the winds reverse (i.e., diverge). Such rising air motion in the atmosphere tends to increase condensation and rainfall.
• Suppressed rainfall phase: winds converge at the top of the atmosphere, forcing air to sink and, later, to diverge at the surface. As air sinks from high altitudes, it warms and dries, which suppresses rainfall.
• It is this entire dipole structure, that moves west to east with time in the Tropics, causing more cloudiness, rainfall, and even storminess in the enhanced convective phase, and more sunshine and dryness in the suppressed convective phase.

Jhelum River
• The Jhelum has its source in a spring at Verinag in the south-eastern part of the Kashmir Valley. Hence statement 1 is incorrect.
• It flows northwards into Wular Lake (north-western part of Kashmir Valley). From Wular Lake, it changes its course southwards. At Baramulla the river enters a gorge in the hills.
• The river forms steep-sided narrow gorge through Pir Panjal Range below Baramula. Hence statement 2 is correct.
• At Muzaffarabad, the river takes a sharp hairpin bend southward.
• Thereafter, it forms the India-Pakistan boundary for 170 km and emerges at the Potwar Plateau near Mirpur.
• After flowing through the spurs of the Salt Range it debouches (emerge from a confined space into a wide, open area) on the plains near the city of Jhelum.
• It joins the Chenab at Trimmu.
• The river is navigable for about 160 km out of a total length of 724 km.