Tag Archives: Planet Earth

How do we know what materials the interior of the Earth is made of if the farthest we have dug is 8 miles?

One of the main ways we have learned about the earth’s interior is by studying earthquakes.

Scientists have learned a lot about how vibrations (which is what earthquakes are) travel through different types of materials (solids, liquids, semi-solids.) 

Imagine you take a big rock and put your hands on the side of it, while somebody else taps it with a hammer. You would sense different things if the person tapped right next to your hands, or if they tapped further away, or if they tapped on the far side of the rock.  If your hands were really sensitive, and you kept a detail of what you felt, you would learn a lot about that. Then imagine doing the same thing with different materials, maybe a big jello mold, or an inflated basketball, or a bucket of water. You would pretty soon know what kind of vibrations would feel like from different kinds of taps in different places on different materials. 

Scientists have sensors all around the world that measure earthquakes and other vibrations in the earth very precisely. Let’s say a big earthquake happens in Japan, it will be detected in Japan and the nearby region, but also in America, and Australia and Europe. By comparing the types of vibrations detected in those different parts of the world, and looking at how long they took to travel, scientists can infer quite a lot about the types of material that the vibrations were traveling through. 

Then they take information from other scientists who have studied the kinds of stuff the earth is made of, and how those materials behave under heat and pressure. When the different groups of scientists put their data together they are able to form a pretty clear understanding of the composition of the interior of the planet without having to observe it directly.

How do deserts form? Where are those sands coming from?

One of the main factors that turns a normal place into a desert is an absence of water. This prevents plants from growing, and in turn removes the normal process of plants capturing carbon dioxide from the air and converting it into carbon compounds.

Normally those organic compounds plus tiny bits of rock plus water form a sort of glue that keeps the ground together as a form of soil, and then plant roots can sink into it and help keep it into place even better. But no plants or water in a desert means nothing to keep the bits of rock stuck down, and so the next ingredient, wind, takes effect.

Wind picks up the bits of rock and blows them around, and the lightest forms of grit become blown away completely, perhaps out to sea, while the larger, sandy-sized bits more or less stay. So you end up with fairly uniform and often very stable dunes of sand.

And the final piece is rock erosion. Hot sun, cold nights, constant wind abrading away rock faces with blown grit. Over thousands of years it adds up into more crumbling dry rock that eventually forms more sand.

How did the oceans get polluted with mercury?

First, mercury is an important reagent in several heavy chemical industry processes. Waste from such processes is flushed out and eventually reaches sea.

Second, while toxic, mercury has no specific utilization biochemistry pathways. Most organisms never before had to deal with high quantities of heavy metals and never evolved a way to render them harmless. This leads to a) organisms just keep getting more and more mercury, unable to remove it and slowly dying from poisoning and b) mercury staying in water-soluble and bioaccessible form.

To remove mercury from food chain, it needs to be converted to insoluble form, for example, mercury sulfide, which is main mercury ore, cinnabar. Problem is, we can’t do this ourselves just as we can’t simply convert excess CO2 in atmosphere back to coal and oxygen, we don’t have some bacteria to eat it and by itself reaction of free mercury with free sulfur would take literally ages.

As of now we are saved by the fact that ocean is huge and mercury gets diluted below dangerous levels – as long as we do not dump more waste right where we fish.

How do scientists find out the temperature of the earth thousands of years ago?

A proxy is a permanent or semi-permanent record that responds in a known manner to certain environmental variables, and this is what is used by scientists to reconstruct information about the environment (such as temperature) in the past. A huge number of proxies are used by scientists to infer things about the past – which one you use depends on what timespans you are interested in, what environmental variables you are trying to reconstruct, where the region of interest is geographically, and so on.

The question is about thousands of years ago, which is actually very young geologically speaking. The key proxies of interest for these timescales are ice records and tree rings (although others such as corals exist).

Ice cores can be used to reconstruct temperature because the ratio between the two main oxygen isotopes (atoms that are chemically identical but have slightly different masses) depends on a number of factors, including sea surface temperature. If you can control for non-temperature related factors and then use a calibration curve (which we can use known instrumental records over the past few centuries and lab experiments for), then we can use these oxygen isotope ratios to infer temperature.

Tree rings can also be used to reconstruct temperature because the growth of a tree depends on several parameters such as temperature and rainfall in a known fashion. If you know how to calibrate growth patterns for a specific tree species (which you can do by comparing tree ring patterns to known, modern temperature records) then you can in turn infer temperature changes in the past.

How are oases formed in deserts?

Deserts are not ideal place for humans to inhabit. The harsh conditions are not suitable for any creature, let alone humans. Yet, there is something that could make the human habitat possible in the vast sea of sand. Those are the oases. In geological terms, an oasis is an isolated area of fertile land, a patch of vegetation. Would you believe that without oases, the world wouldn’t have been like now? Many great journeys in human history have been through deserts and the travelers wouldn’t have made to the other end of the desert if not for the oases.
An oasis is a green patch of land formed around a water source. This makes possible the growth of vegetation and the development of an ecosystem, albeit small, around it. If it is large enough, the environment also provides living conditions for humans, helping to evolve as a civilization.
There are a number of factors that contribute to the formation of oases that individually or in combination with other factors facilitate the formation. For an oasis to form there should be a water table beneath the land. Depending in the geographical features, the water source can be an underground river or an aquifer or an above ground river in the proximity of the desert. Lakes and seas lying near the deserts are also able to trigger the creation. The water can seep to the surface with enough pressure and form an oasis. Man-made wells are also utilized to access the water in many places.
The oasis formation is also helped by heavy rains and storms in the desert. Since the sand is porous, the rainwater would ooze down the pores and it might be trapped by the various layers of rocks and stones, thus creating a water source for the oasis. Powerful storms displace huge amount of sand which lowers the level of land and bring the waterbed closer to the surface and easily accessible.
The vegetation growth is often aided by the migratory birds who drop seeds which sprout in the presence of water. Date palms, figs, peaches and apricots are amongst the most common plants found in oases. These plants, particularly date palms, help to trap the water further and better the conditions for organic life.
Oases have played important role in the course of trading and cultural exchange between various civilizations, and the progress of human lives. The notable ones include Kharga in Egypt, Tutua in Algeria and Kufra in Libya.
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When and how were the Himalayas formed?

The Himalayas or Himalaya is the tallest mountain range in the world. Literally meaning the ‘abode of snow’ in Sanskrit, this natural wonder has the third largest deposit of snow and ice, after the poles. The Himalayas extend for some 2400 km, spanning Pakistan, India, Nepal, China and Bhutan. It is home for nine of the ten tallest peaks in the world, including Mount Everest, the tallest peak in the world which measures 8848 m. The mountain range is also the source of some major rivers in the world, such as Indus, Ganges and Bhramaputra. Himalaya serves as a natural border of India, and has played a big role in sketching the culture and lifestyle of the subcontinent. Himalaya has great significance in Hinduism and Buddhism.
Despite its amazing superlatives, the Himalaya is comparatively a younger mountain range. In fact, it is one of the youngest, with an age estimated to be around only 50 million years. A lot of research had gone into understanding the formation of Himalayas. It is believed to have been formed as a result of a collision between two tectonic plates, Indo-Australian and Eurasian.
According to German scientist Alfred Wagner’s Theory of Continental Drift, there had been only a single large continent named Pangaea. The landmass then began to break up and move towards and from each other. About 200 million years ago, India was an island floating off the coast of Australia. It was separated from Asia by the Tethys ocean. As Pangaea began to break, the Indian plate began to drift towards Asia in North. It traveled more than 6000 km in a period of 150 million years before finally colliding with the Eurasian plate. The Tethys ocean went out of existence, having been closed by the Indian plate.
When collided, neither of the plates could be subducted because their crusts were of low density. Instead they were folded and faulted along the threshold, forming the Himalayan mountain range. The mountain grew over millions of years, assuming the current form.
The Indian plate is still drifting towards North, with a speed of 67 millimeters per year. As a result, the height of Himalaya is also increasing, with a rate of 5 millimeters per year, though impeded by erosion and gravity. The movement of Indian plate makes the area susceptible to seismic activities. Recurring earthquakes are evidence of the movement, and it will continue to rise in future years. Hence, the area is becoming more dangerous for living. Add to that unscientific construction practices, a catastrophe is waiting to happen.

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Why are hill stations cooler than plains?

People love hill stations. Especially the people living in equatorial regions, where the sun is blazing down on them, do love to take a trip to the beautiful hill stations and spend a couple of days there. The perpetual cold climate is what attracts everyone to the hill stations. But what is the reason behind the relatively colder climate in hill stations even while the plains are scorching in the summer heat?
There are a number of factors that affect the distribution of climate around the world; altitude, winds, proximity of sea, the rotation of earth and so on. The parameter that affects the atmospheric temperature the most is the altitude of the place.
The temperature is closely related to pressure. The first thing you would need to know is that the atmospheric pressure is very low in higher altitudes. This is due to somewhat the absence or the lower amount of air there. The air is actually a combination of various gases such as Oxygen and Nitrogen and water vapor. It has weight, and the atmospheric pressure at a place is simply the force that the air particles exert on that particular place. The gravitational pull of Earth forces the air constituents to be as close to the planet surface as possible. And owing to this, the higher places have a lot less amount of air than the sea level; that is, the density of air is less in higher altitudes. Less density means less amount of gas per unit volume. Since temperature is the average energy of the particles per unit volume, it will be lower in higher regions.
The heating process of Earth also contributes to this phenomenon. The sun doesn’t heat the air directly. It actually heats the surface of Earth. When the surface gets warmed up, it further heats up the layer of air above it. This air gets enough kinetic energy to move and rises up in the air, expanding in volume. The expansion means the decrease in its density. Hence, the temperature would have been reduced by the time they get to higher parts of the atmosphere.
Scientific studies have revealed that the atmospheric temperature register a decline by an average of 6.5 degree Celsius by every 1000 meters. This is called lapse rate. It varies according to regions, though. The other factors such as winds and proximity of sea also affect the temperature.

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What is Geothermal Energy? What is its source?

The world is pursuing new energy sources in the wake of the depletion of fossil fuels and as well as the environmental hazards caused by them. Scientific world is now emphasizing on producing energy from renewable sources, like Sun, tide or wind. There is also another great source of energy that is yet to be utilized in its full potential. That is the Earth itself. The Earth’s interior contains a great amount of energy, stored in the form of heat. This energy is called Geothermal Energy, which manifests itself in the forms of hot springs and geysers.
The origin of geothermal energy is attributed to two facts. The first one is the formation of the planet. For thousands of years, Earth had been a hot, molten sphere. Then it began to cool, which took several thousand years as well. Even though the surface of the planet has attained a liveable state that exists today, the inner side of Earth is still in the cooling process. The inside of Earth is full of molten magma and other fluids. The lava flow during a volcanic eruption is an evidence for this fact. The continuous heat loss from this cooling and the radioactive decay are the sources of the huge amount of energy stored in Earth.

Geothermal energy had been familiar to the world since early ages. Hot springs had been used for bathing since ancient times. There are a number of features for geothermal energy that makes it appealing. A major advantage of it is its renewability. The extraction of geothermal energy is very low, when comparing to the large amount of energy stored inside the Earth. It is also reliable and economical and most importantly causes very low pollution problems. Even though toxic gases and other materials can accompany the extraction of the energy, it is less dangerous than fossil fuels.

Electricity has been produced from geothermal power since early 20th century. The first geothermal power plant was established in Italy in 1904. The United States is the country that produces most amount of power from geothermal energy. It also houses the largest group of geothermal power stations in the world, located in the state of California. The Philippines, Indonesia, Italy, Mexico, Iceland and New Zealand are among the other nations, which number more than 25, those lead the usage of geothermal electricity. The energy is also used directly in various places, for heating, green houses and several industrial processes. The researches for using this gigantic source of power are continuing in full steam.

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What is the difference between Natural Greenhouse Effect and Enhanced Greenhouse Effect?

The Sun is the primary source of energy for Earth. The energy reaches the planet in the form of sunlight. The light, which is an electro-magnetic wave, is mainly composed of infrared rays, visible light and ultraviolet rays. A major portion of the UV rays will be absorbed by the ozone layer around the Earth. The remaining rays will reach the planet along with the visible light and warm the Earth’s surface. These rays are of relatively smaller wavelength. The infrared rays, which have a greater wavelength, will be reflected by the hot surface of Earth.
These infrared rays, which have to escape the atmosphere, are but absorbed by some of the gases in the air. They then re-radiate these rays in different directions, mostly back to the Earth. These rays possess a large amount of energy and cause a rise in the atmospheric temperature. This phenomenon is much like what happens in a natural green house and hence is called the Greenhouse Effect.
The gases which have the ability to absorb the infrared rays are called greenhouse gases. A number of greenhouse gases are naturally found in atmosphere but others are the products of various human activities. Vapor, Carbon Dioxide, Methane, Nitrous Oxide, Ozone and Chlorofluorocarbons are the major greenhouse gases.
The idea of the greenhouse effect was put forward for the first time in 1824. A scientist named Joseph Fourier was the person who gave the first indications of the phenomenon. Another scientist, John Tyndall, took the studies further. He discovered how the heat radiations affect the gases and proved the phenomenon of greenhouse effect scientifically in 1859.
Carbon dioxide is one of the most dangerous among the greenhouse gases. It is a naturally occurring gas but the increasing industrial activities and deforestation are triggering an accelerated rise in the amount of the gas in the atmosphere. The share of carbon dioxide in greenhouse effect is between 9% and 26%.
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Although the Natural Greenhouse Effect is instrumental in preserving the biosphere, its growth leads to Global Warming, which is the result of Human Enhanced Greenhouse Effect. The phenomenon of Global Warming is one of the worst threats to nature now. The atmospheric temperature is on the rise every year. It is the cause of the melting of glaciers in Polar Regions and the rise in sea level, causing strong climatic changes. A number of low-level islands have disappeared and some are about to be drowned. The world nations have now understood the danger of global warming and begun to tackle the emission of carbon dioxide and other greenhouse gases.

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What are the principal layers of the atmosphere of Earth?

The atmosphere is a layer of various gases around Earth that is held by the gravitational force of the planet. It has been formed by the activity over millions of years. Atmosphere regulates temperature and prevents the harmful rays from Sun from entering the biosphere of the planet, thereby providing the livable environment for organisms. Ninety-nine percent of the weight of atmosphere is contained within 100 km distance from Earth. Temperature, pressure and content vary at different places in the atmosphere. According to properties, the atmosphere has been divided into five major layers.

Atmosphere of Earth
Troposphere is the layer of atmosphere that is closest to Earth. It is up to 7 km in Polar Regions and up to 16 km in equatorial regions with an average altitude of 12 km. 2he region constitutes for almost 80% of the mass of the atmosphere. The major climatic phenomena like wind, rain, snow falling, lightning and thunder all take place here. In this region, temperature falls with increase in height. The boundary of the layer is called Tropopause, a region marked by stability in temperature.
Stratosphere stretches between 10 km to 50 km from Earth, above Tropopause. The layer is marked for its lack of clouds and other features of weather. Stratosphere is the most suitable region for air transportation. Here, temperature rises with the increase in distance from the Earth. It also contains the Ozone layer which absorbs the ultraviolet rays and other harmful radiations from the Sun, thereby preventing them from reaching Earth. The Ozone layer stretches between 15 km and 30 km from Earth. It is because of the activity of Ozone layer the temperature in this region increases with altitude.
The layer above Stratosphere is called Mesosphere. The region extends from 50 km to 80 km above Earth. Mesosphere shows a drop in temperature according to the height. It is the coldest region of the atmosphere.
Thermosphere is located above Mesosphere above 80 km of height. This region has high temperature due to the energy from Sun. In Mesosphere, temperature increases according to height reaching as far as to 1500 degree Celsius. Mesosphere also constitutes most part of the Ionosphere as well. It is a region ionized by solar radiation and contains many electrically charged particles. The region is most suitable one for radio communication for it helps the propagation of radio waves.
The outermost layer of the atmosphere is called Exosphere. It stretches between 700 km and 1000 km above the planet. It merges with the outer space and the particles here constantly escape to the space.

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