Class 9 Social Science Part 2 Chapter 1 MCQ – Oceans and Life

Ocean relief, also called submarine relief, includes underwater plains, mountains, ridges and trenches. These features influence habitats, the availability of resources and the movement of ocean water.

The continental shelf extends gently beneath the sea from a continent. Its shallow waters often support abundant marine life, and its seabed may contain oil and natural gas.

Abyssal plains are vast, relatively flat regions at great ocean depths. They differ from steep continental slopes, elevated ridges and the narrow depressions called ocean trenches.

A guyot is a flat-topped underwater mountain, usually a former seamount. Its summit was eroded near sea level and later submerged, leaving a flattened surface beneath the water.

Wind transfers energy to the ocean surface, producing waves. Strong winds can generate large waves. Tsunamis have a different main cause: sudden displacement of water, commonly by undersea earthquakes.

Wavelength measures the horizontal distance between successive crests or troughs. Wave height is the vertical distance from trough to crest, so these two measurements describe different features.

Waves enlarge cracks into caves and may cut through a headland to form an arch. Its roof can collapse, leaving a stack, which further erosion reduces to a stump.

Waves can deposit sand and other sediments along the shore, forming beaches. Sea caves, arches and stacks develop mainly through erosion, which removes material from coastal rocks.

During this alignment, solar and lunar tidal effects reinforce each other. The tidal range becomes larger, with higher high tides and lower low tides. “Spring” does not refer to a season.

Neap tides occur around the first and third quarters of the Moon. The solar and lunar tidal effects partly offset each other, reducing the difference between high and low tide.

A large ship needs enough water beneath its hull to avoid running aground. High tide raises the local water level, allowing safer passage through some shallow channels and harbour entrances.

These coastal areas have tidal conditions that offer potential for energy development. Tidal energy uses moving seawater, although the chapter explains that it is not yet widely used across India.

Ocean currents respond to winds, Earth’s rotation, differences in temperature and salinity, and the shape of continents and ocean basins. Political boundaries do not physically drive ocean water.

The Gulf Stream carries warm water from lower latitudes into the North Atlantic system. The Labrador Current carries colder water along eastern Canada, showing how currents can influence nearby coastal temperatures.

trient-rich conditions support marine food chains.
Explanation: Mixing in such regions can make nutrients available to tiny marine organisms. These support larger food chains, including fish, which helps explain the importance of many current-meeting regions for fishing.

Cyclones develop from atmospheric disturbances over warm ocean waters. Tsunamis commonly result when an undersea earthquake displaces water. Their causes differ, although both can seriously threaten coastal communities.

Ocean Bottom Pressure Recorders detect changes associated with passing tsunami waves. Their data help confirm the threat after seismic instruments identify an earthquake, supporting the wider warning process.

A warning is useful only if people receive it, understand it and know what to do. Training and practice help coastal communities evacuate promptly and follow emergency instructions.

GEMINI receives satellite information and transfers it to mobile phones through Bluetooth. Its application provides useful marine advisories and warnings, helping fishing communities make safer decisions while at sea.

Bathymetry describes the depths and shape of underwater terrain. It helps people understand seabed features and supports navigation, scientific study and planning for activities in oceans and other water bodies.

Seaweed is a living organism and belongs among marine biological resources. Petroleum, natural gas and gravel are non-living resources, although they may also be obtained from marine environments.

Tides, waves and wind are naturally replenished sources of energy. Oil and natural gas are finite fossil fuels, while sand and gravel are materials rather than renewable energy sources.

The Blue Economy combines economic development and improved livelihoods with the protection of ocean ecosystems. Its aim is to use marine resources sustainably so that benefits continue in the future.

SDG 14 focuses on conserving oceans and using marine resources sustainably. The chapter connects it with reducing pollution, protecting ecosystems, regulating fishing and conserving marine areas.

he territorial sea extends up to 12 nautical miles from the baseline. The coastal country has sovereignty there, subject to rules such as innocent passage for foreign ships.

The 24-nautical-mile limit is measured from the baseline, not added to the territorial sea. In this zone, a country has limited powers to enforce certain laws.

An EEZ extends beyond the territorial sea to a maximum of 200 nautical miles from the baseline. Resource rights do not amount to complete ownership; lawful navigation by other countries continues.

Innocent passage allows peaceful transit through territorial waters. It must not harm the coastal country’s peace, good order or security, and it does not authorise activities such as unauthorised fishing.

The high seas do not belong to one country. States enjoy freedoms such as navigation, subject to international obligations. Cooperation is necessary to address overfishing, pollution and safety.

COLREGs guide safe vessel movement through lookout, speed and signalling rules. MARPOL addresses pollution from ships. Together, such agreements help protect people, trade and the marine environment.