La Nina is a climatic pattern that refers to the cooling of the ocean surfaces along the tropical west coast of South America. During this weather pattern, warm ocean water and clouds move westwards increasing the chances of places like Indonesia and Australia getting much more rain than usual. These fluctuations tend to leave the regions of southwestern U.S. extremely dry.

The most severe La Nina occurrence in recent history was the 1988-89 event, which led to a seven-year drought in California. La Niña is a complex weather pattern that occurs every few years, as a result of variations in ocean temperatures in the equatorial band of the Pacific Ocean, The phenomenon occurs as strong winds blow warm water at the ocean's surface away from South America, across the Pacific Ocean towards Indonesia. As this warm water moves west, cold water from the deep sea rises to the surface near South America; it is considered to be the cold phase of the broader El Niño–Southern Oscillation (ENSO) weather phenomenon, as well as the opposite of El Niño weather pattern. The movement of so much heat across a quarter of the planet, and particularly in the form of temperature at the ocean surface, can have a significant effect on weather across the entire planet.

Tropical instability waves visible on sea surface temperature maps, showing a tongue of colder water, are often present during neutral or La Niña conditions.

La Niña events have occurred for hundreds of years, and occurred on a regular basis during the early parts of both the 17th and 19th centuries. Since the start of the 20th century, La Niña events have occurred during the following years:


Credit :  Wikipedia 

Picture redit : Google 


Keystone species play a unique and crucial role in the functioning of an ecosystem. The animals and organisms that come under this category help to maintain biodiversity within their community either by controlling populations of other species that would otherwise dominate the community or by providing critical resources for the survival of a wide range of organisms.

These species act as the glue that holds the system together. The term was coined by Dr Robert Paine in 1969, to describe the power a single species exerts on an ecosystem. Examples of keystone species include starfish, sea otters, beavers, wolves, elephants, prairiedogs and bees.

Keystone Species Examples

Sea Otter

The sea otter (shown below) is considered a keystone species as their consumption of sea urchins, preventing the destruction of kelp forests caused by the sea urchin population. Kelp forests are a critical habitat for many species in nearshore ecosystems. In the absence of sea otters, sea urchins feed on the nearshore kelp forests, thereby disrupting these nearshore ecosystems. However, when sea otters are present, their consumption of sea urchins restricts the sea urchin population to smaller organisms confined to protective crevices. Thus, the sea otter protects the kelp forests by reducing the local sea urchin population.

Large Mammalian Predators

While small predators are important keystone species in many ecosystems, as mentioned above, large mammalian predators are also considered keystone species in larger ecosystems. For example, the lion, jaguar (shown below), and gray wolf are considered keystone species as they help balance large ecosystems (e.g., Central and South American rainforests) by consuming a wide variety of prey species.

Sea Star

Sea stars (shown below) are another commonly recognized keystone species as they consume mussels in areas without natural predators. In many cases, when the sea star is removed from an ecosystem, the population of mussels proliferates uncontrollably, and negatively effects the resources available to other species within the ecosystem.

Credit :  Biology dictionary  

Picture Credit : Google 


A landfill is a dumping ground for waste materials. It is the systematic disposal of garbage or trash by burying it in the ground. Most modern landfills are designed in a way that they reduce contamination of the nearby groundwater and soil. Nowadays, they are also completely sealed to prevent the methane that is generated by the decomposing waste from diffusing in the environment.

How Do Landfills Work?

Modern landfills are built using a layering system designed to safely isolate waste and monitor any byproducts, leaks and anything else that can harm the environment. Isolating the trash from air and water is vital for preventing contamination.

We can learn more about how landfills work by examining each layer.

Cells (Old and new)

Each day, trash is compacted a cell in order to make the most of the space available in the landfill. The day’s work cell is also known as the daily workface. Here, trash is organized in layers or lifts then compacted accordingly.

Heavy machinery like bulldozers and compaction equipment are used to compress the trash and place it in the landfill. A six inch layer of dirt covers the cell after it’s made and is then compacted once more. This layer helps contain odors and prevent unwanted pests. Some landfills are considering alternatives like tarps or cement emulsions to save space.

The Liner System

The bottom layer of the landfill consists of a liner that keeps trash and byproducts separate from the environment and groundwater. Some facilities use more than one type, but at any landfill you’ll find at least one of the below liners.

Compact clay liners: These liners are normally made of dense, compacted clay solid enough to prevent waste, liquid or gas leaks from seeping into the environment.

Plastic liners: These liners are made of dense plastic and other synthetic materials, normally 30 to 100 mils thick. Plastic liners are typically used in municipal solid waste (MSW) landfills.

The Drainage System

On top of the liner, you’ll find a storm water drainage system that filters out both the liquids produced by trash and the water collected from rain and snow. This layer is important because it separates produced liquids from solid waste. Another drainage system is used to specifically filter out the liquid produced by trash, called leachate, from any rainwater and the rest of the landfill.

Gas Collection System

The gas collection system uses extraction wells and pipes throughout the landfill to carry landfill gas that’s generated when waste decomposes to treatment areas where it is then vented, burned or converted into energy.


A landfill is permanently capped with a plastic liner when it is full. After it’s capped, the landfill is covered with two feet of soil. Then, vegetation (normally grass and plants without penetrating roots) is planted on top to prevent soil erosion due to rainfall and wind. The landfill is monitored for 30 years to ensure there is no detrimental impact to the environment.

As you can see, today’s landfills are a far cry from the disease-ridden dumps from years before. The industry is also exploring other ways to make landfills cleaner, safer and more environmentally friendly in addition to the processes we’ve already mentioned. See below to learn a few ways landfills are becoming more sustainable.

Credit : Big Rentz

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LED stands for Light-emitting diode. It is a semiconductor device that emits light when an electric current flows through it. Unlike others lights, LEDS never dim with time and have an extended lifespan that can last a couple of years. They also do not contain poisonous gases like mercury that are commonly used to make the traditional lights. These energy-efficient bulbs are made up of glass and aluminum, which can be recovered by recycling and used to create other products.

The LED is a specialised form of PN junction that uses a compound junction. The semiconductor material used for the junction must be a compound semiconductor. The commonly used semiconductor materials including silicon and germanium are simple elements and junction made from these materials do not emit light. Instead compound semiconductors including gallium arsenide, gallium phosphide and indium phosphide are compound semiconductors and junctions made from these materials do emit light.

These compound semiconductors are classified by the valence bands their constituents occupy. For gallium arsenide, gallium has a valency of three and arsenic a valency of five and this is what is termed a group III-V semiconductor and there are a number of other semiconductors that fit this category. It is also possible to have semiconductors that are formed from group III-V materials.

The light emitting diode emits light when it is forward biased. When a voltage is applied across the junction to make it forward biased, current flows as in the case of any PN junction. Holes from the p-type region and electrons from the n-type region enter the junction and recombine like a normal diode to enable the current to flow. When this occurs energy is released, some of which is in the form of light photons.

It is found that the majority of the light is produced from the area of the junction nearer to the P-type region. As a result the design of the diodes is made such that this area is kept as close to the surface of the device as possible to ensure that the minimum amount of light is absorbed in the structure.

To produce light which can be seen the junction must be optimised and the correct materials must be chosen. Pure gallium arsenide releases energy in the infra read portion of the spectrum. To bring the light emission into the visible red end of the spectrum aluminium is added to the semiconductor to give aluminium gallium arsenide (AlGaAs). Phosphorus can also be added to give red light. For other colours other materials are used. For example gallium phoshide gives green light and aluminium indium gallium phosphide is used for yellow and orange light. Most LEDs are based on gallium semiconductors.

Credit : Electronics notes 

Picture Credit : Google 


The Kyoto Protocol was the first significant international treaty that aimed to combat global warming. It was named after the city (in Japan) in which it was adopted in December 1997.

It urged participating countries to develop national programmes to reduce emission of greenhouse gases (like carbon dioxide and methane). It came into effect only in 2005 after delayed approval. Since 1997, 191 countries have backed the agreement. However, some developed countries including the US, Canada, and Russia have denied meeting the emission targets.

While the Kyoto Protocol expired in 2020, the Paris Agreement is now the active instrument to fight climate change.

The Kyoto Protocol is based on the principles and provisions of the Convention and follows its annex-based structure. It only binds developed countries, and places a heavier burden on them under the principle of “common but differentiated responsibility and respective capabilities”, because it recognizes that they are largely responsible for the current high levels of GHG emissions in the atmosphere.

In its Annex B, the Kyoto Protocol sets binding emission reduction targets for 37 industrialized countries and economies in transition and the European Union. Overall, these targets add up to an average 5 per cent emission reduction compared to 1990 levels over the five year period 2008–2012 (the first commitment period).

In Doha, Qatar, on 8 December 2012, the Doha Amendment to the Kyoto Protocol was adopted for a second commitment period, starting in 2013 and lasting until 2020.

As of 28 October 2020, 147 Parties deposited their instrument of acceptance, therefore the threshold of 144 instruments of acceptance for entry into force of the Doha Amendment was achieved.  The amendment entered into force on 31 December 2020.

The amendment includes:

New commitments for Annex I Parties to the Kyoto Protocol who agreed to take on commitments in a second commitment period from 1 January 2013 to 31 December 2020;
A revised list of GHG to be reported on by Parties in the second commitment period; and
Amendments to several articles of the Kyoto Protocol which specifically referenced issues pertaining to the first commitment period and which needed to be updated for the second commitment period.

Credit : United nations climate change 

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