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Groundwater moves in pore space. The flow in a porous medium (subsurface) occurs between particles (sand, silt, gravel, etc. or a mix of these).


Groundwater moves in pore space. The flow in a porous medium (subsurface) occurs between particles (sand, silt, gravel, etc. or a mix of these).


If porosity (porous volume in a given subsurface volume) is high, groundwater moves fast as a rule of thumb. A simple velocity definition is provided for groundwater flow analysis. It is discharge velocity or specific discharge. It is defined as water discharge through a representative area of porous medium/representative total area.

Similar to surface flow, water flows from higher elevations to lower elevations in the subsurface as groundwater flow.


Carbon is released into the atmosphere as carbon dioxide and methane, two greenhouse gases contributing to climate change. Carbon is also stored in photosynthetic vegetation, which we are removing.


  1. global cycling of carbon
    The image below shows a simplified carbon cycle.
    You can read about the carbon cycle in detail here.

  2. relevance to the issue of global warming
    Carbon exists in various forms, one of which is carbon dioxide. The relationship between carbon dioxide and global warming is explained fully here.

Carbon also exists as methane, which is another greenhouse gas contributing to climate change.

Forests are typically carbon sinks, meaning they store carbon. When they are removed, they release carbon into the atmosphere. Thus, deforestation contributes to increased amounts of carbon in the atmosphere and increased warming.

There is also the potential for feedback effects. For example, as the planet warms, the rate of decomposition will increase soils will release more carbon dioxide into the atmosphere.

To conclude, the carbon cycle and global warming are intimately connected, and a change in one portion of the carbon cycle leads to changes elsewhere. Burning fossil fuels removes carbon from the soil and releases it into the atmosphere. Removing trees, which take in carbon dioxide during photosynthesis, releases more carbon dioxide into the atmosphere. These disruptions and others to the carbon cycle are key drivers of global warming and anthropogenic climate change.


Yes plants undergo adaptive evolution just like animals.


The evolution or change in organisms can be observed in nature.
The existing genetic variation provides natural selection with the material needed for changes in the population.


In the desert, plants that have glossier leaves will be better adapted to the dry conditions in the desert environment. As the climate changes the varieties of the plant with less glossy leaves were unable to survive and reproduce as well as plants with more glossy leaves. This will create a change in the population. This is an example of adaptive evolution.

A classic example in animal adaptive evolution is the peppered moth in England. Before the Industrial Revolution the peppered moth population was primarily white with a small minority of black moths. During the Industrial Revolution and the extensive use of coal the black variety was better adapted to the changing environment. After the use of coal sharply declined with the use of electric power, the white variety again was better adapted. The population went from mainly white, to mainly black, to back to mainly white.

Natural selection can only select from existing variations, Presently observed changes in the existing variations are all results of a loss of genetic information. Examples such as bacterial resistance , (see the Beak of the Finch page 260), resistance to malaria, and the blind fish of Death Valley are all due to the loss of genetic information.

Both animals and plants are subject to adaptive evolution and genetic changes due to loss of genetic information. Note Darwinian evolution is an unobserved extrapolation of the observed adaptive evolution.


To generate electricity.


Geothermal electricity, is generated from water heated from geothermal activity rising and moving a turbine than powers a generator.
This hot water is then either recycled, which is done by cooling it and then putting it back into the pipes that lead into the ground, Or it is used in local houses to heat them.

Geothermal energy is widely used in areas of geothermal activity, such as Iceland, where it is a renewable source of power and has almost no carbon footprint (the only bit being the construction of it).
There is also a lot of research in this way of generating electricity, so it is becoming more efficient and cheaper to set up all the time.

The only disadvantages of it is that it can be costly to set up, the geothermal activity can reduce or disappear, dangerous substances can surface and it has a small chance of triggering earthquakes.


study of local geology, geophysics methods, bore logs and some luck :)


Drilling for water can be a challenging job in many areas due to the uncertainty in the presence of water and the depth of the water table.

The first step is to study the local geology using the available geological maps to look for structures that will likely host water.

A classic example of such structures is a layer of permeable rock (such as sandstone or fractured limestone) underlined by impermeable levels (such as clay ). The water will accumulate within the permeable layer.

Sometimes the permeable level is sandwiched between two impermeable levels and the water in it can be pressurized so that the well will spontaneously flow at surface. It is an "artesian" aquifer. The recharge of such aquifer happens from lateral formations that convey the infiltrated rain water towards the permeable level.

Geophysics methods can be used to identify the presence of water at depth. They are based on the changes in electric conductivity caused by the water.

Finally bore holes can be drilled to assess the geological sequence of the strata and to identify layers potentially able to host an aquifer.

It is fair to admit that some degree of luck is often associated with finding water mostly in complex and challenging geological settings.


Well, we're hurting it through climate change, development, hunting, pollution, habitat loss and degradation, and invasive species.


Currently, we're in the sixth mass extinction. Since humans established a dominant presence on the planet, the rate of species extinction has risen to between 1,000 and 10,000 times the normal rate.

Here are a few causes:

Climate Change : Change in temperatures and precipitation globally (including and especially in oceans) have led many species, who are are unable to keep up with the rapidly changing conditions, to go extinct.

Structures and industrial development : In the last 50-100 years, the US has built dams in almost every place it could. Dams prevent natural migrations of fish, build up sediment in places where it shouldn't be, increase flooding, and decrease soil nutrition content in areas downstream of it.

This has led to the extinctions of a plethora of species, many of which we haven't even been able to identify. However, a lot of them have a large impact on the ecosystem's health and the diversity of species.

Hunting : The number of animals we've hunted to extinction or near extinction is astonishing. Even in the many cases where measures were taken to prevent the extinction of a species, such as with many of animals in Africa (lions, cheetahs, rhinos, elephants, etc.), the decreased population of these animals has proven to be very detrimental to their ecosystems, greatly decreasing their species diversity, and thus the health of the ecosystem.

Over-fishing is another significant reason why we have hurt species diversity. You can read about it here and here.

Pollution : Between the oil spills, mining runoff and byproducts, fertilizer and agricultural runoff, industrial waste, not to mention the coal, natural gas, and oil we have been burning since the industrial revolution, this is a significant way we have impacted species diversity. The number of species that have been severely damaged or forced to extinction by the pollutants we emit in the air and water is pretty staggering.

Habitat loss and degradation : While connected to impacts mentioned above, humans have substantially altered the surface of the earth through urbanization, building of infrastructure, expansion of agriculture, and resource consumption. This has lead to major changes and loss of habitat. Habitat is degraded when roads cut through forests, when light pollution from cities invades natural darkness, when selective logging occurs, and so forth.

introduction of invasive species : Whether purposefully or accidentally, humans have introduced non-native species to new habitats and at times this has had drastic consequences. Invasive species often have no predators or controlling population effects and thus out compete natural species. For example, cane toads are linked to species extinctions and the Guam broadbill is now extinct in part due to invasives.

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