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  2. Coal mining - Wikipedia

    en.wikipedia.org/wiki/Coal_mining

    Coal mining is the process of extracting coal from the ground or from a mine. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from iron ore and for cement production.

  3. Carbon dioxide - Wikipedia

    en.wikipedia.org/wiki/Carbon_dioxide

    Carbon dioxide content in fresh air (averaged between sea-level and 10 kPa level, i.e., about 30 km (19 mi) altitude) varies between 0.036% (360 ppm) and 0.041% (412 ppm), depending on the location. [46] In humans, exposure to CO 2 at concentrations greater than 5% causes the development of hypercapnia and respiratory acidosis. [47]

  4. Deep sea mining - Wikipedia

    en.wikipedia.org/wiki/Deep_sea_mining

    Deep-sea mining is not governed by a universal legal framework. Various norms and regulations have emerged both at an international level and within individual countries. The United Nations Convention on the Law of the Sea (UNCLOS) sets the overarching framework. The United States did not ratify the founding treaty. [93]

  5. Macau - Wikipedia

    en.wikipedia.org/wiki/Macau

    Macau [e] or Macao [f] is a special administrative region of the People's Republic of China (PRC). With a population of about 710,000 people [12] and a land area of 32.9 km 2 (12.7 sq mi), it is the most densely populated region in the world.

  6. Caste system in India - Wikipedia

    en.wikipedia.org/wiki/Caste_system_in_India

    The poverty level in India's lowest castes dropped from 49 percent to 39 percent between 1995 and 2005, compared to a national average change from 35 to 27 percent. The life expectancy of various caste groups in modern India has been raised; but the International Institute for Population Sciences report suggests that poverty, not caste, is the ...

  7. Ethereum - Wikipedia

    en.wikipedia.org/wiki/Ethereum

    Ethereum is a peer-to-peer network that maintains a database containing the storage values of all Ethereum accounts and processes state-altering transactions. [57] Approximately every 12 seconds, a batch of new transactions, known as a "block", is processed by the network.