Task 7, 8

The last two tasks are to demonstrate the processes leading to climate changes and their consequences. Floating ice, according to Archimedes‘ principle, balances with the buoyancy of water, so the ice on the surface of the ocean (the water in the bowl) does not affect the amount of the level after melting, but the water inflow from the mainland (the edge of the bowl) increases the water level in the ocean. The melting of ice in the Arctic Ocean does not affect the level of the ocean, while the melting of mountain and mainland glaciers (e.g. in Greenland) affects the level. This so-called glacioeustasy, i.e. melting of ice or water binding to mainland and mountain glaciers, led to a level of fluctuation in the geological history of about 100 m to the current state.

The last experiment is to demonstrate the existence and release of carbon dioxide into the atmosphere. If we place the pieces of limestone into a wider beaker and pour the vinegar over it (possibly diluted HCl, if the experiment is only demonstrative and performed by a teacher, the experiment is more spectacular), CO2 bubbles begin to develop. That it really is CO2 can be proved by a small floating candle which we lay burning on the surface after the beginning of the experiment. After a few minutes, the level of CO2 rises above the surface. The candle should go out because it needs oxygen for burning. It is possible to deduce from the experiment that when ventilation of some rocks (limestone) or (and also) the combustion of organic matter (paraffin candles), carbon dioxide is produced, which is an important greenhouse gas. The teacher should explain to pupils that the amount of CO2 in the atmosphere and its absorption or release through the rock environment and the plant cover are one of the most important factors influencing the climate on Earth. Therefore, in the geological past there were also situations when the Earth was completely frozen apart from a thin belt along the Equator („Snowball Model“ – the land as a snowball in the Precambrian), or the climate was generally more balanced and warmer, when the tropical zone was significantly wider than at present („Greenhouse Model„ – countries with temperate climate and leafy woods up to the Poles in the Eocene).