Earth Science

The Earth's surface and crust are constantly evolving due to the rock cycle, which describes the continuous transformation of rocks through processes like melting, cooling, erosion, and sedimentation.

Sedimentary rocks are formed through the natural process of lithification, which involves the compaction and cementation of sediments over time. The other options do not describe the formation of sedimentary rocks.

Garnet is a mineral, not a rock. It is commonly found as individual mineral crystals and is used as an abrasive and gemstone.

Mauna Loa is one of the largest active volcanoes on Earth, located in Hawaii. It is well-known for its frequent eruptions, which classifies it as an active volcano.

The coldest point in the atmosphere is the mesopause, which is the boundary between the mesosphere and the thermosphere. Temperatures there can drop to around -90°C, colder than at the tropopause or exopause.

The Moon's gravitational pull is the primary force that causes tides in Earth's oceans. While the Sun also affects tides, its influence is less than that of the Moon. Galaxies and meteorites do not have a significant effect on ocean tides.

Marble and slate are both metamorphic rocks formed from the transformation of limestone and shale, respectively, under heat and pressure. This process changes their mineral structure without melting them, classifying them as metamorphic rocks.

Atmospheric temperature increases at higher altitudes due to a temperature inversion, where a layer of warmer air lies above cooler air, reversing the normal temperature decrease with altitude. This phenomenon is called 'inversion,' not convection.

During a volcanic eruption, the volcano emits solid materials (like ash and rocks), liquid lava, and gases (such as sulfur dioxide and carbon dioxide). Therefore, the material includes solid, liquid, and gaseous forms.

Earthquakes are primarily caused by the movement of tectonic plates, which create stress and release energy in the Earth's crust. While landslides and volcanic eruptions can be associated with earthquakes, they are not the main cause of earthquakes themselves.

The Earth completes a full 360° rotation in 24 hours. Dividing 360° by 24 hours gives 15° per hour, which is the degree of rotation of the Earth each hour.

Approximately 97% of the Earth's water is salt water, primarily found in oceans and seas. This makes option C the correct answer.

The South Atlantic Ocean rarely experiences tropical cyclones due to unfavorable conditions such as cooler sea surface temperatures and stronger vertical wind shear, unlike the Western Pacific, North Atlantic, and Indian Ocean where tropical cyclones are common.

Volcanoes can form at 'hot spots' due to mantle plumes, which are upwellings of hot mantle material that melt through the crust to create volcanic activity independent of tectonic plate boundaries.

Volcanoes commonly occur at divergent plate boundaries where plates move apart, convergent plate boundaries where plates collide, and at hotspots which are volcanic regions fed by underlying mantle plumes. Therefore, all these locations are typical for volcano formation.

The troposphere is the lowest layer of Earth's atmosphere where all weather occurs and where humans breathe. The other options are either incorrect atmospheric layers or unrelated terms.

Weather and climate are primarily driven by solar radiation, which provides the energy that powers atmospheric processes. Earth's internal heat and gravity have minimal direct impact on weather and climate patterns.

Earthquake waves travel faster in solid, rigid materials like rock because these materials transmit seismic energy more efficiently than fluids or loose materials. Among the options, 'Flexible rock' (corrected spelling) is the best choice as waves travel slower in water, air, or soil.

The elastic rebound theory explains the causes of earthquakes by describing how stress builds up in rocks until they suddenly break and release energy, causing an earthquake.

The age of the solar system is widely accepted by scientists to be about 4.5 billion years, based on radiometric dating of meteorites and Earth rocks. This makes option C the correct choice.

The troposphere is the lowest layer of Earth's atmosphere where almost all weather phenomena occur, including clouds, rain, and storms. Other layers like the stratosphere, mesosphere, and thermosphere do not have weather.

The troposphere contains about 75–80% of the atmosphere's mass because it is the lowest layer where most of the air molecules are concentrated due to gravity. This makes it the densest atmospheric layer compared to the stratosphere, mesosphere, and thermosphere.

The mesosphere extends approximately from 46 km to 85 km above Earth's surface. This range is widely accepted in atmospheric science, making option A the most accurate choice.

A planet retains its atmosphere when its gravity is strong enough to hold the atmospheric gases and when the temperature is low enough to prevent the gases from escaping into space. High temperature increases gas velocity, making it easier for gases to escape, while strong gravity helps retain them.

The troposphere is the lowest layer of Earth's atmosphere and extends from the planetary surface up to the bottom of the stratosphere. This boundary is known as the tropopause.