World Wetlands Day - 02 February 2014

Those people that know me know that I love stomping around in wetlands.  Every year I, introduce hundreds of students (and a few adults) to the world of aquatic macroinvertebrates.  I have hundreds of photos of wetland animals and plants.  One of my favorite books is Swampwalker's Journal: A Wetlands Year by David M. Carroll.

I mention all of this because of what is occurring this Sunday (02 February).  February 2nd is commemorated each year as World Wetlands Day in honor of the adoption of an international Convention on Wetlands at Ramsar, Iran on 02 February 1971. 

 
The Ramsar Convention works to identify and preserve Wetlands of International Importance.  Michigan is home to one of these wetlands.  The Humbug Marsh is located along the  Detroit River in southeastern Michigan and is part of the Detroit River International Wildlife Refuge.

Snow Dunes

Many of the schools in the area are closed again today due to blowing and drifting snow.  As I was driving to work earlier this week I noticed how the snow was acting like sand and forming the same types of dunes that would be found in sand.  Under the right conditions, snow can act very much like sand - cold (well below freezing) temperatures that do not allow the snow to melt , fine "dry" snow crystals that do not easily stick together, and of course wind.

I went out into the open field behind the Conservation District office and photographed these small snow "dunes".  None of these features was more than a few inches in height, but they display the classic features of certain types of dunes.

The first feature is a barchan dune.  Barchan dunes form in open areas where there are no obstructions.  A barchan dune is shaped like an arch with the curve of the arch pointing into the wind and arms extending downwind.  In this first picture, there are two barchan dunes on the right half of the image.
 

Snow "dune" features - Barchan dunes to the right of the image

Here is the same image with the wind direction indicated with an arrow and the dunes highlighted with curved lines.  The dunes slowly move downwind an particles are picked up from the face of the dune and deposited on the arms or in the lee space created behind the peak of the dune.

Snow "dune" features - note wind direction (arrow) and barchan dunes (arcs)

Over time, the arms of barchan dunes will intersect with those of adjacent dunes.  The resulting undulating line of dunes in now known as a barchanoid dune. 

Snow "dune" features - barchanoid dune in center of image

Here is the same image with wind direction and dune indicated.  The barchan dunes from image 1 and 2 are to the right of this picture.

Snow "dune" features - note wind direction (arrow) and barchanoid dune (curving line)

Eventually, barchoid dunes will begin to lose their undulating curves and become straight or nearly straight lines.  This type of dune is known as a transverse dune.  Often many transverse dunes will be found together in rows of ridges and valleys.

This image shows the transition between barchanoid and transverse dune forms.  The closest formation still shows the undulating character of a barchanoid dune, but the dunes doing off into the distance have straightened out forming a series of ridges perpendicular to the wind.

Snow "dune" features - transverse and barchanoid dunes

Another copy of the same image with wind direction and dunes indicated.  the nearest line is a barchoid dune and the further lines have evolved into straighter transverse dunes.

Snow "dune" features - note the wind direction (arrow), barchanoid dune (closest line), and transverse dunes (furthest three lines)

For more information on these and other dune types visit the Great Sand Dunes National Park website.

Winter rabbit sign

During Winter, many small animals become very secretive.  With the leaves being gone from most plants they become extremely wary.  Some species retreat to the space beneath the snow - the area known as the "subnivean zone".  Other species become mainly nocturnal to hide from the eyes of daytime predators, but in some ways Winter makes it easier to tell that these animals have been around.

One of these animals is the Eastern Cottontail Rabbit (Sylvilagus floridanus).  While the Eastern Cottontail  is one of the most common mammals in Eastern North America, it can be difficult to see just how common they are.  They prefer brushy areas where they can hide from their many predators.  Because they browse on leafy vegetation, their feeding often goes unnoticed.  Being small and light (less than 5 pounds) they rarely leave tracks.

However, Winter exposes the lives of Cottontail Rabbits. It becomes easier to see what they are eating and where.  Without green vegetation, the diet of rabbits switches to twigs, bark, and buds.  The rabbits use their sharp incisors to strip bark from small branches and trunks.  If enough bark is removed, this has the potential of killing the plant. 

Cottontail Rabbit sign - stripped bark and clipped branches near the snow line

However, rabbits often get blamed for damage that they do not cause.  Any bark removed by a rabbit will be above the snow line (to a height of about 18 inches).  You can often tell how high the snow was during the previous winter by looking for rabbit damage.  On the other hand, damage right at ground level was probably caused by mice or voles.  When mice or voles chew on trees in the Winter it often goes unnoticed because it occurs in that subnivean zone below the snow.

Cottontail Rabbits have been feeding heavily on this clump of shrubs

In addition to removing the bark, rabbits often leave another sign of their feeding - branches that are neatly clipped off at an angle.  Deer also eat the ends of branches, but because they lack upper incisors the branches that they eat will have a torn or jagged appearance where they twisted or ripped them off.

Branches eaten by Cottontail Rabbits are neatly clipped at an angle

Another sure sign of Winter cottontails is their scat.  Rabbit droppings will appear as piles of dried, brown spheres containing shredded plant fibers.  These droppings look very much like cocoa puffs.  Because their digestive system does not do a good job of processing all the nutrients in the plants, rabbits will often eat their own droppings so the contents can be digested a second time.

Rabbit droppings - Do not eat the cocoa puffs!

A third sign of rabbits that winter makes visible is their tracks.  Snow exposes the movements of rabbits and allows us to track their paths of travels.  While Cottontail rabbits have large feet (in proportion to their body size) that allow them to travel across packed snow, they do not like moving through deep fluffy snow any more than most other mammals.  They usually will stick to well defined paths or runs of packed snow under these conditions. These runs (and individual tracks away from the runs) are easy to see and show us where the rabbits travel between food sources and cover. 

A partially drifted in rabbit run leading to an isolated shrub.

We are not the only species capable of recognizing rabbit runs.  Birds of prey also notice the paths made by rabbits and will often perch over them waiting for an unsuspecting Cottontail to make a move.  If you follow rabbit runs, sometimes you will find places where a hawk or owl stooped down to take a rabbit.  A patch of disturbed snow with wing makes, some fur, and a few spots of blood are often all that indicate a successful kill.

This well used rabbit path runs for dozens of yards in a nearly straight line between patches of cover.

A little bit of snow cover and knowledge of the signs to look for makes it easy to determine if Cottontail Rabbits are around and can help remove some of the mystery from the species' habits.

NOT a Sign of Spring

I saw this scene today at Nelson Park in Mt. Pleasant.

It's obviously a flock of birds in a tree, but what kind of birds?  Maybe this next picture will make it clearer...

The Space Shuttle Challenger - Twenty-eight years later

Tomorrow (January 28th) marks the twenty-eighth anniversary of the Space Shuttle Challenger disaster.  On January 28th, 1986 at 11:39:13 EST, the Challenger broke apart 73 seconds after liftoff when an O-ring in one of the solid rocket boosters failed.  All seven crew members died in the accident.

I remember watching the accident at school.  I was in 5th Grade at the time.  I don't remember if we were supposed to watch the launch or if the teacher brought in a television after the accident happened.

Officially titled STS-51L, this mission of the Challenger was scheduled to be a special one.  STS-51L was carrying a teacher into space.  In 1984, NASA began the Teacher in Space Project (TISP) to inspire students and ignite interest in math, science, and space exploration.  More than 11,000 teachers applied for the program.  Sharon "Christa" McAuliffe was selected to be the first Teacher in Space (with Barbara Morgan as her backup).  McAuliffe (and Morgan) trained for 5 months for the mission.  Once the Challenger reached space, McAuliffe was scheduled to teach two lessons to students back on Earth.  On here return back to Earth, McAuliffe was supposed to go back to teaching in the classroom.

The destruction of the Challenger and the death of seven crew members was a big blow to NASA.  Because of the presence of a non-professional (McAuliffe) on the flight, Challenger had received more press attention than most previous Shuttle flights.  NASA cancelled flights of the remaining Space Shuttles for nearly three years to examine safety issues and determine the cause of the accident.  The Teacher in Space Project was officially replaced with the Educator Astronaut Project in the 1990s.  

Barbara Morgan would eventually make it to space.  She retired from teaching in 1998 and went to work at NASA as a full-time employee.  She flew as a mission specialist on STS-118 in August 2007.

For more information on STS-51L please visit the official NASA website.  Information on Christa McAuliffe and Barbara Morgan can be found on their official NASA bios.

Technically, those are BIRD feeders, technically...

We feed the birds in our neighborhood all Winter long.  There has been snow on the ground here for the past six weeks so the birds seem to be more dependent than they have been during the past few years, especially the ground-feeding birds like Dark-eyed Juncos and Mourning Doves.  We also get large mixed flocks of finches, as well as Black-capped Chickadees, Northern Cardinals, White-breasted Nuthatches, Blue Jays, Downy Woodpeckers, Red-bellied Woodpeckers, and a few more occasional visitors.

However, these seem to be the most prominent visitors to the feeders...

Fox Squirrels enjoying the bounty laid before them.

Nobody likes a free lunch as much as a Fox Squirrel.

Although there are only four squirrels in this photo, we have counted as many as nine squirrels on and around the feeders.

For more info on Fox Squirrels, check out this post I wrote last February.

Geology Concepts - Cross-bedding

Continuing with the geology theme...

Yesterday I wrote about the geologic principle of Original Horizontality.  This is the idea that the sediments that formed sedimentary rocks were originally deposited horizontally, even if the rocks are no longer in a horizontal position.  These horizontal layers are known as beds. These beds are typically found over wide areas and are uniformly thick.

However, sometimes the sediments within those beds are not laid down evenly in a horizontal layers.  The sediments within a bed may be laid down in inclined layers.  This process is known as Cross-bedding.  Cross-bedding happens when sediment is moved by water (or wind) currents.  Cross-bedding is often found in dunes, ripples, and sand/gravel bars.  Cross-bedding in sedimentary rock provides evidence of past currents preserved in stone.

Looking at a photo from Pictured Rocks National Lakeshore, most of the beds found in the exposed sandstone are horizontal, just as they were originally deposited.  There are several beds in which the sediments were not deposited horizontally.  These beds show cross-bedding and are evidence of currents moving the sediments around.

Sandstone beds at Pictured Rocks National Lakeshore - Can you find the cross-bedding?

The next image is the same photograph with some of the cross-bedding indicated by tilted yellow lines.  If you look closely, there are several more areas of cross-bedding that I have not marked.

Sandstone beds at Pictured Rocks National Lakeshore - areas of cross-bedding are indicated by diagonal lines

The next photograph is another image of sandstone deposits at Pictured Rocks National Lakeshore.  The horizontal beds are easily visible, as is one section of cross-bedding.

Horizontal and cross-bedding at Pictured Rocks National Lakeshore

Here is the same photograph with the cross-bedding outlined. 

Sandstone formation at Pictured Rocks National Lakeshore - area of cross-bedding outlined

The above photographs are taken at Pictured Rocks National Lakeshore.  Pictured Rocks is located in Michigan's Upper Peninsula along the southern shore of Lake Superior.  This is about a 4 1/2 hour drive from Mid-Michigan. 

Why didn't I just use photos of a rock formation from Mid-Michigan instead?

There is no surface bedrock to be found in Mid-Michigan.  Most of the bedrock in Michigan is covered by glacial deposits of sand, gravel, and rock.  These deposits range from a few inches in some area to up to 1200 feet.  The State of Michigan estimates that the average depth of glacial deposits in Michigan is 300 feet!