World Geography - 4 (Gen. Studies)

Rocks are made up of various minerals. Out of about 2000 different minerals, only 12 minerals are common all over the world. These 12 rock forming minerals are called 'rock formers'.

Statement (1) is correct. Igneous rocks are the first one to be formed. All other rocks are formed by subsequent work of various rock forming processes and factors over these rocks. Thus, igneous rocks are also called parent rocks.
Statement (2) is correct. Unlike sedimentary rocks, igneous rocks do not have any strata.
Statement (4) is also correct. In the absence of pores in the igneous rocks, water does not penetrate in these rocks easily. Hence, igneous rocks are less affected by chemical weathering.
Statement (3) is wrong. Sedimentary rocks are not the most widely distributed rocks on the earth’s surface.

The inclination of the earth's axis to plane of the orbit is 23½°.

Lapse rate is the rate of change in temperature with increase in altitude.

An ecosystem is defined as a functional system comprising both living (biotic) components and the physical environment (abiotic factors) in which they interact. This includes organisms, their habitat, and the complex relationships between them. Options C and D describe unrelated acoustic and atmospheric phenomena respectively, while option A refers to taxonomic classification rather than ecological systems.

Savannah climate is characterized by seasonal rainfall with a long dry season and sparse precipitation, supporting bush and short grass vegetation (A-4). Humid subtropical climates have no prolonged dry season and reinforced vegetation due to consistent moisture (B-2 in option A, but described as B-3). West coast marine climates have moderate rainfall around 75cm annually without pronounced dry seasons and support forest vegetation (C-3 or C-5). Middle latitude deserts receive minimal rainfall below 15cm with thorny scrub vegetation (D-1). Option A appears to be the intended answer despite some description inconsistencies.

The biosphere is the highest and most comprehensive level of ecological hierarchy, encompassing all living organisms and their interactions with Earth's systems. A biome is a large ecosystem type. A community is populations of different species. A population is individuals of one species.

The first international conference for globalizing the environmental problems was held at Stockholm.

Correct answer is (1). 

Correct Answer: Sirocco

Earth's revolution around the sun, combined with its 23.5° axial tilt, causes seasonal changes throughout the year. Different parts of Earth receive varying amounts of sunlight intensity as it orbits, creating the four seasons. Days and nights are caused by Earth's rotation on its axis, not its revolution around the sun.

The Bushmen (also known as San people) are indigenous to Southern Africa and traditionally inhabit the Kalahari Desert region spanning Botswana, Namibia, and South Africa. The Thar Desert is in India/Pakistan, Atacama is in South America, and Great Victoria is in Australia - none of these are Bushmen territories.

Correct answer is (2). 

Transhumance is the seasonal movement of livestock and herders between fixed summer and winter pastures. It typically involves moving animals from valley floors in winter to high mountain pastures in summer, then back again. This is distinct from nomadic migration (which is more permanent) or ranch movements.

Ocean currents are driven by three primary factors: Earth's rotation creates the Coriolis effect, wind patterns move surface water, and differences in water density (from temperature and salinity variations) cause vertical movement. Earth's revolution around the sun creates seasons but does not directly cause ocean currents. Therefore, only factors 1, 2, and 3 are correct.

The Indian Ocean is indeed warmer than both the Atlantic and Pacific oceans in northern and southern hemispheres due to its location between warm land masses. Among major oceans, the Atlantic is the coldest in the equatorial region because of upwelling and circulation patterns. However, the Pacific's average surface temperature is NOT higher than the Atlantic's in the southern hemisphere - the Atlantic is actually warmer there. Therefore, only statements 1 and 3 are correct.

Agulhas Current is the major warm current in the Indian Ocean.

The time between two high tides averages 12 hours and 25 minutes, not exactly 12 hours. This is because the Moon takes approximately 24 hours and 50 minutes (not 24 hours) to return to the same position relative to Earth's surface, so the tidal cycle is half of that period. Option B would be the time between high and low tide, not between two high tides.

Laterites are soil types rich in iron and aluminium, formed in hot and wet tropical areas. Nearly all laterites are rusty-red because of iron oxides. They develop by intensive and long-lasting weathering of the underlying parent rock.

Laterite soil is formed in hot, wet tropical areas through intensive leaching - heavy rainfall washes away soluble minerals like silica and lime, leaving behind insoluble iron and aluminum oxides. This gives laterite its characteristic red/orange color. Black soil (regur) is a volcanic soil rich in clay, not formed through leaching.

The correct matching is: Asia has the Gobi Desert (4), Africa has the Kalahari Desert (3), North America has the Mojave Desert (2), and South America has the Atacama Desert (1). These are all major desert systems located on their respective continents. The Atacama is one of the driest places on Earth, the Kalahari is a semi-arid savanna, the Mojave is a cold desert in North America, and the Gobi is a large cold desert in East Asia.

The correct matching is: Stalactites form in limestone caves (2), Solanchak soils are saline/sodic soils (1), Shott (or Chott) refers to salt lakes in North African deserts (4), and Sills are intrusive igneous rock formations (3). Stalactites and stalagmites require limestone, Solanchak is a type of saline soil, Shotts are characteristic salt features in arid regions, and sills form from magma intrusion between rock layers.

 Faulting helps in the formation of rift valley.

A caldera is a large collapsed depression formed when a volcano erupts and empties its magma chamber, causing the ground above to collapse downward. This creates a crater much larger than typical volcanic vents. Calderas are not lava types, small mouths, or necessarily multi-vented volcanoes - they are specifically the collapsed basins left after massive eruptions.

Magma is called lava when it reaches the Earth's surface (crust). Magma is the molten rock beneath the surface, while lava is the same material once it erupts and flows on the surface. The core and inner portion are too deep, and mantle is where magma originates.

Volcanic eruptions produce materials in all three states of matter: solid (pyroclastics like ash and rocks), liquid (lava/molten rock), and gas (water vapor, CO2, sulfur dioxide). This makes option C the correct answer.

The age of Earth is estimated to be approximately 4.54 billion years (with an error margin of about 1%), based on radiometric dating of meteorites and Earth's oldest rocks. This method measures the decay of radioactive isotopes like uranium-238 into lead-206. The oldest terrestrial minerals (zircons) are about 4.4 billion years old, consistent with this age.

The outer core of the earth’s interior is in molten state while the inner core is in solid state. At some point of depth in the earth's interior, around 5150 km, is the transition from the liquid outer core and the solid sphere of the inner core, a ball of incredibly hot iron-nickel alloy. Temperatures here reach between 5,000°C and 7,000°C, and pressures are calculated to be around 3,000,000 units of sea level atmospheric pressure. Despite the high temperature, at these pressures, the metals cannot remain molten.

The mantle extends to 2900 km, is the thickest layer, and is composed of silicate rocks rich in iron and magnesium. All statements are correct.