Science With Mr. Milstid

One of the most important, but often overlooked, aspects of the world around us is the weather. It has an impact on everything in our lives – from what we wear day to day, to whether or not we are able to eat!

So what is it, really?
Weather is the condition of the atmosphere at a certain time and place. It is affected by the amount of wind, moisture, pressure and temperature in the air.

In order to fully understand weather, we need to be able to understand wind.
Wind is, very simply, moving air. It is also one of the driving factors of weather – it causes and carries weather phenomena from place to place.

What causes wind?
Wind is caused by the uneven heating and cooling of the earth’s surface - both globally and locally.

For instance:
As solar energy reaches the Earth, areas around the equator heat up more than the poles. Air in this region expands as it warms, creating areas of low air pressure, which rise. The warmer the temperature of air, the lower the pressure.
Air around the poles receives less solar radiation, and are cooler than air around the poles. These regions of cooler air condense, sink and create areas of high air pressure. The cooler the temperature of air, the higher the air pressure.

Wind is created by the convection that occurs as a result: low pressure (warmer) air rises; High pressure (cooler) air sinks, and rushes in to fill the space left by the rising low pressure air.

So our definition of wind, then, can be changed to: air moving from areas of high pressure to areas of low pressure.
Incidentally, the greater the difference in pressure (and temp) between two pockets of air, the higher the force/speed of wind.

The atmosphere is a layer of gases surrounding the Earth. But, it is also much more.
It is a moving source of life for every creature of the planet. While the atmosphere is mainly composed of nitrogen (N₂), it also contains gases such as oxygen (O₂) and carbon dioxide (CO₂) that plants and animals need to survive.
It has specialized molecules like ozone (O₃) that filter out harmful radiation from space.
The atmosphere also protects us from the vacuum of space. Without the atmosphere, our world would be as barren and dead as the Moon or Mercury, not to mention extremely cold!

 

Atmospheric Composition
The atmosphere is made up of just a few main molecules:

The rest of it is made of things called trace elements like water vapor, ozone, and other particles and molecules floating around.

Layers of the Atmosphere
There are 5 layers in the atmosphere.
From the earth up, they are:

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere

Almost all weather occurs in the Troposphere, the lowest layer of the atmosphere, which extends from the surface up to 8 to 16 kilometers above Earth’s surface (lowest toward the poles, highest in the tropics). Earth’s surface captures solar radiation and warms the troposphere from below, allowing it to be habitable.

Temperatures in this layer decrease with elevation/altitude (by about 6.5°C with each kilometer of altitude).

At the top of the troposphere is the Tropopause, a layer of cold air (about -60°C), which forms the top of the troposphere and creates a “cold trap” that causes atmospheric water vapor to condense.

The next atmospheric layer, the Stratosphere, extends upward from the Tropopause to 50 kilometers. In the Stratosphere temperatures increase with altitude because of absorption of sunlight by stratospheric ozone.
(About 90 percent of the ozone in the atmosphere is found in the stratosphere in a section called the Ozone Layer. The Ozone Layer is important because it absorbs harmful UV radiation, preventing it from reaching the surface of the earth.)

At the top of this layer is the Stratopause, where temperatures peak at about -3°C.

In the third atmospheric layer, the Mesosphere, temperatures once again fall with increasing altitude, to a low of about -93°C.

Above this layer is the Thermosphere, where temperatures again warm with altitude, rising higher than 1700°C.

The highest layer of the atmosphere is the Exosphere. This layer is not well defined: it blends into space.

Figure 1 below shows the pattern of temperature fluctuations across layers of the atmosphere.

Figure 1. Structure of the atmosphere

See larger image

Source: © 2006. Steven C. Wofsy, Abbott Lawrence Rotch Professor of Atmospheric and Environmental Science, lecture notes.

Atmospheric pressure in the atmosphere changes with elevation consistently across all layers of the atmosphere: as elevation increases, pressure decreases because the total weight of air above you lowers.
Figure 1 illustrates this trend as well. This fact is what causes pressure changes in your ears while flying in an airplane.

Mount Pinatubo: Predicting a Volcanic Eruption



 
Mount Pinatubo: Aftermath of a Volcanic Eruption

1. Was the Mount Pinatubo eruption a non-explosive or explosive eruption?
2. Based on your observations, what type of volcano is Mount Pinatubo? On what evidence do you base your answer?
3. Over what type of plate boundary is this volcano located? Is this tectonic setting consistent with your answer to the first question?
4. Because volcanologists were able to accurately predict the timing of this eruption, the lives of hundreds of people who evacuated the nearby area were probably saved. What evidence did the scientists observe that prompted them to call for an evacuation?

1. What problems did the inaccurate eruption forecast of the Tungurahua volcano cause for the people of Ecuador and what difficulties might this cause for community officials in the future?
2. What three variables do scientists monitor when attempting to forecast volcanic eruptions?
3. What are some of the hurdles that volcanologists face when trying to make accurate eruption forecasts?

1. Based on your observations of this video and previous videos you have seen, what type of volcanoes are Kilauea and the other Hawaiian volcanoes? On what evidence do you base your answer?
2. Does Hawai’i experience non-explosive or explosive eruptions?
3. Explain Hawaii’s setting in terms of plate boundaries. What makes it so unusual?

1. Describe what is happening throughout the eruption. What kind of material is being ejected by the volcano? Do you see lava? What happens to all of the ash?
2. Based on your observations, what type of volcano produced this eruption? On what evidence do you base your answer?
3. Based on the before and after images, identify ways in which both the volcano and surrounding area were changed by the 1980 eruption.
4. Based on the satellite images, how has the affected area changed in the time since the eruption?
5. What are some similarities and differences in the destruction caused by effusive and explosive eruptions? What, if anything, was surprising to you about the blowdown, lahar, and pyroclastic flow images?
6. What factors play a part in the recovery of vegetation (and wildlife) in areas affected by volcanic eruptions?

The article below is taken from Discovery.com

Toxic Gases Caused World’s Worst Extinction
Michael Reilly, Discovery News

Feb. 4, 2009 — An ancient killer is hiding in the remote forests of Siberia. Walled off from western eyes during the Soviet era and forgotten among the endless expanse of wilderness, scientists are starting to uncover the remnants of a supervolcano that rained Hell on Earth 250 million years ago and killed 90 percent of all life.

Researchers have known about the volcano — the Siberian Traps, for years. And they’ve speculated that the volcanic rocks, which cover an area about the size of Alaska, played a role in runaway global warming that led to the end — Permian mass extinction, the worst dying the planet has ever seen.

Now a team of researchers led by Henrik Svenson of the University of Oslo in Norway have performed a series of experiments, showing the volcano employed an arsenal of deadly weapons during its 200,000-year-long assault on the biosphere.

Prime among them was carbon. Searing magmas from the volcano intruded into the Tunguska Basin in eastern Siberia, a region laden with thick deposits of coal, oil and gas. Heat from the molten rock baked the hydrocarbons, turning the area into the world’s largest fossil fuel-burning plant. In all, the volcano may have belched as much as 100,000 gigatons of carbon into the air (all of humanity emits about eight gigatons of carbon annually).

That’s more than enough to cause a global climate apocalypse. But the team also wanted to know what happened when lava infiltrated the area’s abundant salt deposits. When heated in a laboratory to 275 degrees Centigrade (527 degrees Fahrenheit), the salts released a host of toxic gases, chief among them methyl chloride, an efficient ozone-killer.

“This is the first geologically realistic evidence that ozone collapse during the end-Permian could have actually happened,” Svenson said.

But there is still a lot of uncertainty surrounding the findings, Linda Elkins-Tanton of the Massachusetts Institute of Technology said.

“There is evidence of a large number of genetic mutations in the fossil record around this time,” she said, which could be the result of an onslaught of ultraviolet radiation due to a weak ozone layer. “But the idea of ozone destroyers is pretty new. The question is whether or not the eruptions were powerful enough to inject gases into the stratosphere.”

The answer may come from close examination of hundreds of pipe-like structures strewn throughout the Tunguska Basin. Often 300 meters (984 feet) in diameter, Svenson’s team believes the pipes are ancient volcanic craters left over after the lethal mix of carbon and chlorine gases exploded into the atmosphere.

The article below is taken from The LA Times

Mt. Redoubt volcano’s ‘unrest’ recalls 1989 eruption
Pete Thomas, LA Times

February 3, 2009 — The latest from the Alaska Volcano Observatory on the status of Mt. Redoubt: “Unrest at Redoubt Volcano continues. Seismic activity remains elevated above background.”

Sounds like a broken record, but at least Mt. Redoubt is providing ample warning and has all of Alaska on alert.

Longtime residents surely recall a five-month stretch that began in late 1989 during which the 10,197-foot volcano provided a string of eruptions and a steady outpouring of smoke and ash.

A United Press International article that Dec. 15 featured this initial announcement: “Redoubt Volcano southwest of Anchorage shook with thousands of small earthquakes Thursday, then erupted and shot a cloud of ash seven miles high.”

Farther down in the story: “The eruption followed 24 hours of constant warning tremors, which calmed down after the eruption ended, then picked up again…. The ash plume — which shot 35,000 feet above the two-mile-high mountain — was carried toward Anchorage by strong winds… But the ash cloud skirted Anchorage and dusted towns beyond the city.”

A day after a second, more violent eruption occurred that Dec. 17, the Associated Press reported: “Haze from the volcano drifted over Anchorage, Alaska’s largest city with more than 200,000 people. The debris caused power outages, disrupted air travel and triggered public-health warnings.”

But it was Christmas week and the economy was not in shambles. Shoppers, according to the report, filled “the streets and malls over the weekend.”

Volcanoes, by definition, are areas of the earth’s surface that allow hot, molten rock, ash, and gases to escape from below the surface.

Volcano Parts
All volcanoes have the following parts in common:

• Magma Chamber: A pool of molten rock that forms under a volcano
• Vent: Openings in the earth’s crust that magma flows through.
• Crater: The main opening at the top of a volcano.

Click the image below for a more in-depth interactive tutorial of volcano parts from the National Park Service.

Volcano Activity
All volcanoes fall into 1 of 3 main categories:

1. Active Volcanoes: volcanoes that erupt regularly, or show signs of erupting soon.
2. Dormant Volcanoes: volcanoes that have not erupted in some time, but may again in the future.
3. Extinct Volcanoes: volcanoes that have not erupted in recorded history, and probably will not again.

Where Volcanoes Form
Most volcanoes occur at or near the edges of tectonic boundaries.
The same tectonic motion that causes earthquakes, causes volcanic formations and eruptions.
The interactive map below shows the relationship between tectonic boundaries and the locations of earthquakes around the world. Click on “plate boundaries” and “volcanoes” and take note of the overlap.

Along tectonic plates, there are 3 main areas where volcanism occurs:

• Hot spots
• Rift Zones
• Subduction Zones.

HotSpots
Hot Spot volcanoes occur far from the edges of plates.
Columns of rising magma push through the surface of the earth, forming land and volcanoes

Rift Zones
Rift Zones are places where tectonic plates are moving away from one another (think: divergent boundary).
As plates separate, an opening is created for magma to move toward the surface.

The animation below shows a mid ocean ridge rift zone in action

Subduction Zones
When two converging tectonic plates collide, one (the least dense of the two, e.g. oceanic crust in a continental-oceanic collision) is pushed below the other; it is subducted.
The subducted crust melts as it moves downward through the earth, producing a pool of magma.

The animation below shows a variety of volcanic formations in action. Click the buttons at the top for an up-close view. Pay special attention to the following animations: “Hot Spot Volcanoes,” and “Continental Volcanic Arc” (which is a continetnal-oceanic subduction zone).

Types of Volcanoes
We will discuss 3 main types of volcanoes in our study of volcanism:

• Shield Volcanoes
• Cinder Cone Volcanoes
• Composite Volcanoes

Each type has unique physical characteristics, caused by the way it erupts, and, to some extent, the way it forms.

Shield Volcanoes
These volcanoes are very broad with large bases. They are made of thin layers of lava from repeated slow, gentle eruptions.
They are most common in oceanic areas. As a result, huge explosions can occur when their lava makes contact with ocean water.

Cinder Cone Volcanoes
Steeply sloped sides made of layers of ash and loose rock.
Erupt violently, releasing huge amounts of ash, gas and volcanic material.

Composite Volcanoes
Most common type of volcano.
Broad bases, get steeper toward the top.
Form from explosive eruptions, followed by quiet lava flows. This makes layers of ash and rock that get covered by layers of lava.

Volcanic Eruptions
Regardless of the “type” of volcano, there are 2 main kinds of eruptions:

• Non-explosive
• Explosive

There are many subdivisions of these categories, but we will focus on these two throughout our study.

Non-Explosive Eruptions
These eruptions are relatively calm, and produce slow, gentle flows of lava. They are associated (primarily) with shield volcanoes.

Explosive Eruptions
Explosive eruptions are violent volcanic eruptions.
During an explosive eruption, hot debris, ash and gas shoot out of a volcano - this is, obviously, incredibly dangerous.

Causes of Volcanic Eruptions
When pressure and temperature build up inside of a volcano (due to magma formation inside the volcano), eruptions occur. As the temperature of magma and the gases that occupy a magma chamber builds, their particles begin to spread out (consider the behavior of matter during a state change), and they become less dense (and more buoyant). The pressure of gas dissolved in magma, combined with its decreasing density causes it to rise, making its way to the surface and exiting a volcano in the form of lava or pyroclastic material (see below).

The type of eruption depends on the composition of the magma inside the volcano:

• If there is a lot of water in the magma and silicate in the magma, a non-explosive eruption will occur.
   
  
   
• If the magma in a volcano has a high water and silicate content, an explosive eruption is likely.
   
  

Types of Volcanic Material
When volcanoes erupt, much more than just lava may come out!
There are 4 types of lava that can be erupted from a volcano:

1. AA (ah-ah) Lava
2. Pillow Lava
3. Blocky Lava
4. Pahoehoe (Puh-hoy-hoy)

Explosive eruptions also result in pyroclastic material: lava that is blasted into the air and hardens quickly.

Pyroclastic materials include:

• Volcanic Blocks: huge lava boulders that fall back to earth.
• Volcanic Bombs: giant lava stones.
• Lapilli: lava rocks.
• Volcanic Ash: small pieces of lava that solidify in air and create dust.