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When the location is angled towards the sun, it gets longer days and higher temperatures. When angled away, days are shorter and cooler.


The earth rotates on an axis but the North-South axis is not "vertical" but tilted slightly. As the earth orbits the sun, the axis doesn't change.

The Northern Hemisphere faces the sun while the Southern Hemisphere is facing away from the sun. Temperatures north of the equator will be higher and the days will be longer.

The Northern and Southern Hemispheres face the sun equally.

The Northern Hemisphere faces away from the sun while the Southern Hemisphere faces toward the sun. Temperatures north of the equator will be lower and days will be shorter.

The Northern and Southern Hemispheres face the sun equally.


More info: NASA SpacePlace


Generally when a mineral's surface reflects light we say that it has luster.


Before we look at specific minerals let’s explore what exactly we mean when we say something "has luster".

When it comes to minerals there are two major types of luster: metallic and nonmetallic.


First, we have metallic luster (we refer to these as the metallic minerals). The minerals that we say have metallic luster are opaque (you can't see through them) and shiny. A good example of a mineral that has metallic luster is gold.

enter image source here
Gold nugget.

Courtesy of: Chris Ralph; Obtained from: en.wikipedia.org Public Domain

The metallic minerals have one subcategory which we call submetallic minerals they exhibit submetallic luster. These minerals look like metals however due to weathering and corrosion they’ve become dull or less reflective, cinnabar is a good example of submetallic luster.

enter image source here

Courtesy of: H. Zell (Wikipedia User); Obtained from: en.wikipedia.org Reused under: CC BY-SA 3.0


The second type of luster is nonmetallic luster (we call these minerals the nonmetallic minerals). Minerals that have nonmetallic luster, unlike their metallic counterparts, don't look like metals. Since nonmetallic minerals don't look like metals identifying them is a little less straightforward than identifying a metallic mineral. Lucky for us though scientists have divided the nonmetallic minerals into four subcategories. Without further ado, the three subcategories:

Adamantine (or Diamondlike) this first subcategory is probably the most well-known. We say that a mineral is adamantine when it has brilliance (the light it reflects appears really bright) and shine. They can be transparent or translucent (some light can pass through them but you can't see through them). Adamantine minerals are typically found at jewelry stores, a diamond is a good example.

enter image source here

Courtesy of: Steve Jurvetson; Obtained from: en.wikipedia.org Reused under: CC BY 2.0

Minerals in the second subcategory, Dull (or Earthy) luster, can be tricky to identify. Minerals that we describe as having a dull luster reflect light poorly (you'll probably have pick up the mineral, put it under bright light, and take a close look to see that it does indeed reflect some light) and have a porous and coarse surface. A good example of a mineral with dull luster is a type of clay called kaolinite.

enter image source here

Courtesy of: Rob Lavinsky; Obtained from: www.irocks.com Reused under: CC BY-SA 3.0

Vitreous luster, our third subcategory, is probably the most common type of luster. Vitreous means "glass-like", and like glass these minerals don't reflect vivid light like the minerals in the adamantine subcategory. Minerals that have vitreous luster can be transparent or translucent. Quartz is a great example of a mineral that has vitreous luster.

enter image source here

Courtesy of: JJ Harrison; Obtained from: en.wikipedia.org Reused under: CC BY-SA 2.5

Our fourth and final subcategory of nonmetallic minerals displays what we call Greasy luster. Minerals that are categorized as greasy luster minerals look like they've been coated in grease or oil and can feel "greasy" (or really smooth, almost slippery) when touched. Opal is probably one of the more common examples of a mineral with greasy luster.

enter image source here

Courtesy of: Daniel Mekis; Obtained from: en.wikipedia.org Reused under: CC BY-SA 3.0

I hope this helped!


  • With a few exceptions, Sub-Saharan Africa is not doing well.
  • War has terrible effects on a country's infrastructure.
  • Groundwater overdraft is a growing danger in some of the most populated parts of the world.


In the shorter term, we need to make sure that safe drinking water is available within walking distance of people's homes and that it is free from contamination by sewage bacteria.

On this table of data from 2015 , the WHO/UNICEF monitoring program listed these four countries as having the lowest percentage of rural access to improved water sources:

You can see some of the regional patterns on [this map]

enter image source here
(https://www.wssinfo.org/data-estimates/maps/) .

Some regions, like the islands of Papua New Guinea and dry plains of Mongolia, have geography that makes it difficult to find deep underground water or to collect rainwater. But notice that some of the worst problems are in countries that have experienced war in the recent past. For example, Angola was in a civil war from 1975 to 2002.

The GapMinder website can help you explore some of the data available. For example, I made this graph comparing child mortality rates to the availability of clean water outside of the cities.

Also, have a look at the World Health Organization fact-sheet about drinking water safety .

In the longer term (but not too long!), we need to worry about groundwater overdraft .
Scientific American


Many of the most populated parts of the world are using up groundwater at rates enormously faster than it can be replenished from the surface. The water supplying farms of the central US may in fact be a non-renewable resource .


A Mediterranean climate.


Los Angeles is classified as a warm Mediterranean climate. A Mediterranean climate is a specific type subtropical climate characterized by a dry summer, with a rainy season in the winter, and moderate changes in temperature between the seasons (you won't need a winter coat).

The summer months in LA are typically hot and very dry (it usually doesn't rain during the summer and temperatures exceed #80^oF# [#27^oC#]).

Winter months are mild and snow is incredibly rare however temperatures usually fall below freezing on at least one night per year.

Despite the fact that winter is LA's rainy season, LA averages only 15 inches (381 millimeters) of rainfall annually (to put things in perspective the average annual rainfall for all US cities is 30.2 inches [767 millimeters]).

Below is an image of an abating storm -red sky at night, sailors' delight!

enter image source here
Image is my own work; feel free to reuse in any way except for commercial purposes

LA also experiences a weather phenomenon known as the Santa Ana winds (the locals call them "Santa Anas").

Santa Anas are strong (40 mile per hour [or 64 kilometers per hour] plus), hot, dry winds that blow from east to west (us weather nerds like to call them katabatic winds). These winds are the result of cold air from Canada moving into the high desert regions of the Great Basin (Nevada and Utah) which displace the hot dry air to southwest into the lower-lying region of Southern California. These weather events usually last for about a week or so.

This isn't Los Angeles (it's San Diego a large city about 100 miles south of LA) but the same concept applies, this was taken during a rare wintertime Santa Ana.

enter image source here
Image is my own work; feel free to reuse in any way except for commercial purposes

Santa Anas typically occur, but aren't specifically relegated to, the final months of the summer and are common through the end of autumn (though they can occur at any time of year). These winds result in a dramatic increase in temperature (in the summer temperatures can reach #110^oF# [#43^oC#] and in the rare event that one occurs in the winter temps can exceed #90^oF# [#33^oC#]). Along with an increase in temperature Santa Ana's cause a drop in humidity (typically below 10%, it literally feels like you're getting sandblasted).

Another picture showing the effect of Santa Anas the change in the sky's color is actually due to the particulate matter being blown around (ironically this picture was taken on the same night as the previous one)

enter image source here
Image is my own work; feel free to reuse in any way except for commercial purposes

The image of the palm tree in the article I wrote here.

Thanks to the dry climate wildfires are a constant threat to Los Angeles and Southern California which can easily get out of hand. Luckily Southern California has firefighting crews who work tirelessly to combat and prevent them from occurring and spreading.

LA has variable terrain which aids in the creation numerous microclimates throughout the Los Angeles region. In the summer months the inland valleys to north (such as Laurel Canyon and Studio City) can be as much as #30^oF# (#17^oC#) warmer than the coastal regions (such as Santa Monica) due to the lack of onshore flow (winds that blow from the ocean). The converse is typically true for the winter months where the temperatures in the coastal regions are typically warmer than those in the inland valleys. These valley areas are typically dryer than the coastal regions year-round because the surrounding hills can inhibit fog, which is also common not just in LA but in all of coastal California, from settling in the region as readily as in coastal regions.

The two images below are prime examples of the oh-so-ubiquitous California fog (I wasn't driving, don't use your phone while driving, for cereal don't).

enter image source here
Image is my own work; feel free to reuse in any way except for commercial purposes

enter image source here
Image is my own work; feel free to reuse in any way except for commercial purposes

I know this is a lot of info but I hope it helps!


Soil formation.


Chemical weathering is generally the most active and effective weathering process. Water within soil or stone dissolves minerals of soil, softens minerals that absorpb the water, and dissolves carbondioxide. The dissolved #CO_2# produces carbonic acid, acidifies the water (pH<7) (neutral water has a pH of 7), and increases its solvent action.

Atmospheric oxygen combines with iron in minerals and forms iron oxides. These reactions increase the rates of decaying of many dark colored minerals that have remarkable iron in them. All of the reactions enroling in chemical weathering will produce in the soil solution many dissolved ions from the weathering minerals.


A bay is the term used to describe a recessed area off of the coast that is connected to the ocean or a lake. Bays can be produced or formed a few ways.


A bay is the term used to describe a recessed area off of the coast that is connected to some sort of larger body of water. It is a body of water that is partially surrounded by land.

A gulf is a large bay with a more narrow mouth, a fjord is a steep bay that was shaped by glaciers, and a cove is a small bay with a narrow entrance. In the images below, Wineglass Bay and Ha Long Bay below both are connected to the ocean whereas Emerald Bay is connected to a lake (Lake Tahoe).

Wineglass Bay, Australia

Emerald Bay, US

Ha Long Bay, Vietnam

Bays can be produced or formed a few ways. Plate tectonics is behind the largest bay in the world, the Bay of Bengal. Bays are also formed by erosion of the coast and by glaciers.


You can read more about bays and how they are formed here.

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