Wikipedia The water cycle, also known as the hydrologic cycle or the hydrological cycle, describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly constant over time but the partitioning of the water into the major reservoirs of ice, fresh water, saline water and atmospheric water is variable depending on a wide range of climatic variables. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, surface runoff, and subsurface flow. In doing so, the water goes through different forms: liquid, solid (ice) and vapour.
The water cycle involves the exchange of energy, which leads to temperature changes. When water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment. These heat exchanges influence climate.
The evaporative phase of the cycle purifies water which then replenishes the land with freshwater. The flow of liquid water and ice transports minerals across the globe. It is also involved in reshaping the geological features of the Earth, through processes including erosion and sedimentation. The water cycle is also essential for the maintenance of most life and ecosystems on the planet.
- Hits: 13
Are you worried about climate change? Do you live in the South Hams? Here are some ways to take climate action in the South Hams.
Take action in how you shop. Take action in how you travel. Take action by joining groups. Take action by supporting each other. Take action in non-violent protest.
- Hits: 58
Wikipedia A great conjunction is a conjunction of the planets Jupiter and Saturn, when the two planets appear closest together in the sky. Conjunctions occur every 19.6 years, on average, when Jupiter 'overtakes' Saturn in the sky due to the combined effect of Jupiter's approximately 11.9-year orbital period and Saturn's 29.5-year orbital period.
The great conjunction of 2020 will be the closest since 1623. It will occur seven weeks after the heliocentric conjunction, when Jupiter and Saturn shared the same heliocentric longitude. On 21 December at 13:30 UT, Jupiter will be 0.1° south of Saturn and 30° east of the Sun, meaning both planets will be visible in the same telescopic field of view (though they will be distinguishable from each other without optical aid). The two planets will be visible low above the southwestern horizon in the constellation of Capricornus after sunset. From mid-northern latitudes, the planets will be less than 15° in altitude, one hour after sunset.
- Hits: 153
Wikipedia The iron cycle (Fe) is the biogeochemical cycle of iron through the atmosphere, hydrosphere, biosphere and lithosphere. While Fe is highly abundant in the Earth's crust, it is less common in oxygenated surface waters. Iron is a key micronutrient in primary productivity, and a limiting nutrient in the Southern ocean, eastern equatorial Pacific, and the subarctic Pacific referred to as High-Nutrient, Low-Chlorophyll (HNLC) regions of the ocean.
Iron is an essential micronutrient for almost every life form. It is a key component of hemoglobin, important to nitrogen fixation as part of the Nitrogenase enzyme family, and as part of the iron-sulfur core of ferredoxin it facilitates electron transport in chloroplasts, eukaryotic mitochondria, and bacteria. Due to the high reactivity of Fe2+ with oxygen and low solubility of Fe3+, iron is a limiting nutrient in most regions of the world.
Iron exists in a range of oxidation states from -2 to +7; however, on Earth it is predominantly in its +2 or +3 redox state and is a primary redox-active metal on Earth. The cycling of iron between its +2 and +3 oxidation states is referred to as the iron cycle. This process can be entirely abiotic or facilitated by microorganisms, especially iron-oxidizing bacteria. The abiotic processes include the rusting of iron-bearing metals, where Fe2+ is abiotically oxidized to Fe3+ in the presence of oxygen, and the reduction of Fe3+ to Fe2+ by iron-sulfide minerals. The biological cycling of Fe2+ is done by iron oxidizing and reducing microbes.
- Hits: 11
Wikipedia The calcium cycle is a transfer of calcium between dissolved and solid phases. There is a continuous supply of calcium ions into waterways from rocks, organisms, and soils. Calcium ions are consumed and removed from aqueous environments as they react to form insoluble structures such as calcium carbonate and calcium silicate, which can deposit to form sediments or the exoskeletons of organisms. Calcium ions can also be utilized biologically, as calcium is essential to biological functions such as the production of bones and teeth or cellular function. The calcium cycle is a common thread between terrestrial, marine, geological, and biological processes. Calcium moves through these different media as it cycles throughout the Earth. The marine calcium cycle is affected by changing atmospheric carbon dioxide due to ocean acidification.
- Hits: 6
Wikipedia The sulphur cycle is the collection of processes by which sulphur moves between rocks, waterways and living systems. Such biogeochemical cycles are important in geology because they affect many minerals. Biochemical cycles are also important for life because sulphur is an essential element, being a constituent of many proteins and cofactors, and sulphur compounds can be used as oxidants or reductants in microbial respiration. The global sulphur cycle involves the transformations of sulphur species through different oxidation states, which play an important role in both geological and biological processes.
- Hits: 9
Wikipedia The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth. The production of phosphine gas occurs in only specialized, local conditions. Therefore, the phosphorus cycle should be viewed from whole Earth system and then specifically focused on the cycle in terrestrial and aquatic systems.
On the land, phosphorus gradually becomes less available to plants over thousands of years, since it is slowly lost in runoff. Low concentration of phosphorus in soils reduces plant growth, and slows soil microbial growth - as shown in studies of soil microbial biomass. Soil microorganisms act as both sinks and sources of available phosphorus in the biogeochemical cycle. Locally, transformations of phosphorus are chemical, biological and microbiological: the major long-term transfers in the global cycle, however, are driven by tectonic movements in geologic time.
Humans have caused major changes to the global phosphorus cycle through shipping of phosphorus minerals, and use of phosphorus fertilizer, and also the shipping of food from farms to cities, where it is lost as effluent.
- Hits: 7
Wikipedia The oxygen cycle is the biogeochemical transitions of oxygen atoms between different oxidation states in ions, oxides, and molecules through redox reactions within and between the spheres/reservoirs of the planet Earth. The word oxygen in the literature typically refers to the most common oxygen allotrope, elemental/diatomic oxygen (O2), as it is a common product or reactant of many biogeochemical redox reactions within the cycle. Processes within the oxygen cycle are considered to be biological or geological and are evaluated as either a source (O2 production) or sink (O2 consumption).
- Hits: 10
Wikipedia The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmosphere, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmosphere nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems.
The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle. Human modification of the global nitrogen cycle can negatively affect the natural environment system and also human health.
- Hits: 8
Wikipedia The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major component of many minerals such as limestone. Along with the nitrogen cycle and the water cycle, the carbon cycle comprises a sequence of events that are key to make Earth capable of sustaining life. It describes the movement of carbon as it is recycled and reused throughout the biosphere, as well as long-term processes of carbon sequestration to and release from carbon sinks.
Humans have disturbed the biological carbon cycle for many centuries by modifying land use, and moreover with the recent industrial-scale mining of fossil carbon (coal, petroleum and gas extraction, and cement manufacture) from the geosphere. Carbon dioxide in the atmosphere had increased nearly 50% over pre-industrial levels in 2020, forcing greater atmospheric and Earth surface heating by the Sun. The increased carbon dioxide has also increased the acidity of the ocean surface by about 30% due to dissolved carbon dioxide, carbonic acid and other compounds, and is fundamentally altering marine chemistry. The majority of fossil carbon has been extracted over just the past half century, and rates continue to rise rapidly, contributing to human-caused climate change. The largest consequences to the carbon cycle, and to the biosphere which critically enables human civilization, are still set to unfold due to the vast yet limited inertia of the Earth system. Restoring balance to this natural system is an international priority, described in the both the Paris Climate Agreement and Sustainable Development Goal 13.
- Hits: 7
Page 1 of 2