# Presentation: 779618

## Floodplain ManagementSESSION 3

**Stream Systems on**
**Dynamic Earth**
**Glaciation & Erosion Processes**
**Prepared By**
**Donald R. Reichmuth, PhD.**

**Notes:**
Title Page for Session 3

## Glacial & Erosion Framework

**Objectives:**
**Glacial conditions in North America for the last 30,000 years affect river basins and floodplains**
**Rates and processes of erosion, transport, and deposition**
**The production and movement of sediment by the agents/processes of erosion -- water, ice, gravity, and wind  **
**Case study team assignments**

**Notes:**
Glacial & Erosion Framework -- This slide lays out the objectives to be presented in this session.  The instructor should be tell the students what they are going to hear; then present the information and finally tell them what was said.  

## Glaciation & Surface Processes

**Glaciation**
**Alpine Glaciers**
**Continental Glaciers**
**Geomorphology**
**Surface Forming Processes**
**Water**
**Ice**
**Gravity**
**Wind**

**Notes:**
Slide PP3.0-2 Glaciation & Surface Processes -- There are three branches of geology that must be understood if floodplain management is to successfully solve site specific problems. The first branch, Tectonics, was covered in Session 2.  This Session concentrates on Glacial Geology and Geomorphology. The earth’s surface forces, (often not appreciated by the lay public because the processes are often slow and subtle), determine how river basins are sculptured.  

## Northern Hemispheric Glacial Areas16,000 B.P.

**NOTE:**
**	****Portions Of Alaska**
**	****Are Ice Free**

**Notes:**
Northern Hemispheric Glacial Areas --  This slide is a map centered at the North Pole that shows the extent of glaciers at the last glacial maximum 16,000 years ago.  Note that significant portions of Alaska and Eastern Siberia were ice free even though all of Canada and Northern Europe were ice covered.

## Pleistocene Glaciation

**Note:**
**Alpine Glaciers**
**Continental Glaciers**
**Ice Marginal Rivers**
**Alaska Ice Free Area**

**Notes:**
Pleistocene Glaciation -- North American climate during maximum Pleistocene Glaciation 16,000 years ago are shown on this slide. Note the ice free areas in Alaska; the boundary between the Canadian Alpine and Continental Glaciers; the disturbed drainage pattern and the hot, dry area in southwestern U.S. The ice in the area between the two ice sheets became ice-free soon after the climate began to warm.  This melting created an ice-free path from Eastern Siberia to the Lower-48-States.  Adapted from Dott & Batten, 1971

## Glacial Impact Areas

**Notes:**
Glacial Impact Areas --  The extent of areas impacted by glacial activity in the U.S. during the last four glacial periods are shown. Impacts are most extensive in the Great Lakes area while the glaciation was confined to mountainous areas in the West.  Additionally numerous lakes (not shown on the slide) formed in closed basins in the West and along the ice margin. Water to fill the Western Lakes can from increased precipitation and runoff.  The ice marginal lakes changed rapidly as the ice moved and new outlets formed.  Sea level dropped more than 100 meters and the seafloor was exposed along the coasts. Note that the extent of exposed seafloor is much greater along the east coast than along the west coast. Adapted from Flint, 1971

## Preglacial Teays Basin

_**Teays Basin**_
**Overrun By Ice**
**Channel Buried**
_**Ohio River**_
**	****Forms**
**	****Drains Basin**
** **

**Notes:**
Preglacial Teays Basin --  This slide shows the disruption of the River Basins south of the Great Lakes caused by glaciation.  The preglacial Teays River Basin was overrun by the glaciers and the stream channels filled with glacial debris.  The Ohio River formed south of the ice sheets to carry off meltwater and now has became the river that drains the old Teays Basin.

## Western Glacial Lakes

**15,000 B.P.**
**Climate Much Wetter Than Present**
**Large Basins Had Internal Drainage**

**Notes:**
Western Glacial Lakes --  This slide shows the extent of lake formation in the Western U.S. during the last ice age 15,000 years ago. Note glacial lakes had two origins.  The lakes depicted in this slide occurred because there were closed basins available to be filled the increased precipitation.  Other lakes (not shown here) formed in ice-blocked river valleys along the glacial margin. Adapted from Flint, 1071

## Loess

**Wind Blown Silt**
**From Glaciers**
**Rock Flour**
**Stream Banks ****	****	****Stand Vertical**
**	****	****When Stable**

**Notes:**
Loess --  Location and depth of wind-blown silt deposits (Loess) in Central U.S. are shown.  These deposits are up to twenty meters thick and were derived from sediment blown off the floodplains of the Mississippi, Missouri, Illinois and Ohio Rivers.  During glaciation these river systems carried vast amounts of water and sediment. Adapted from Skinner & Porter, 2000

## Glacial ReboundContours In Meters Uplift

**Notes:**
Glacial Rebound -- This slide is a map of Canada that shows the four major drainage provinces (Pacific, Artic, Labrador and Atlantic) and  the extent of glacial rebound that has taken place in the last 10,000 years.  There are two centers of rebound located on the east and west side of Hudson Bay.  Uplift at each center has been about 100 meters. Adapted from various sources.

## Great Lakes Glacial ReboundContours – Uplift per 100 Yrs.

**Notes:**
Great Lakes Rebound --  This slide is a map of the Great Lakes region showing the water shed boundary (topographic divide) that determines what streams flow into the lakes; the numerous moraine features that are located south of the lakes and uplift rate contours for the ongoing glacial rebound.  The rebound starts near the south shores of Lake Michigan and Lake Erie.  The uplift rate steadily increases to the north-northeast until a rate of 1.75 feet uplift per 100 years occurs just north of Lake Superior.  Base map adapted from Farrand, 1988 and Rebound Data from Clark & Persoage, 1970.

## Sea Level Changes

**16,000 Years BP --**
- 	   120 Meters Lower
**6,000 Years BP –**
- 	   Reached Present Level
**Near Future –**
- 	   Expected To Rise

**Notes:**
Sea Level Changes --  This slide shows changes in land area that was exposed in North America at different times.  These changes are primarily due to sea level change.  The conditions shown are: 1) Peak glacial 16,000 years ago when the oceans were 120 meters lower; 2) Present conditions and 3) at peak interglacial times when most of the world’s glaciers have melted.  Because the climate is now warming, the land area exposed should start decreasing and approach peak interglacial conditions.

## Holocene Sea Level Changes

-  **Primary Cause ---**
- 	 **Glacial Melting**
**     ****	****   ****In The**
**Northern Hemisphere**

**Notes:**
Holocene --  This slide is a graph of Relative Sea Level versus Time (the last 18,000 years).  Initially sea level raised rapidly but started to slow about 6,000 years ago.  Note that most of this rise was caused by melting Northern Hemisphere Glaciers.

## Erosion In River Basins

**Controlling Factors:**
**Chemical vs. Mechanical Weathering**
**Temperature**
**Precipitation**
**Basin Gradient**
**Basin Soil/Bedrock Type**
**Tectonic Activity**

**Notes:**
Erosion in River Basins --  This slide summarizes the factors that control erosion in river basins.

## Chemical & Mechanical Weathering

**Notes:**
Chemical & Mechanical Weathering --  This slide is a graph showing the relative importance of Mean Annual Temperature and Mean Annual Precipitation in determining whether Mechanical or Chemical Weathering will prevail.  Higher temperatures and precipitation favor Chemical Weathering while colder temperatures and moderate precipitation favor Mechanical Weathering.  Only slight weathering occurs when the climate is both hot and dry.  Note that Mechanical Weathering is primarily caused by freeze-thaw action that forces small cracks in solid rock to expand thus breaking the material apart. Adapted from Peltier, 1950 

## Erosion Processes

**Notes:**
Erosion Processes (Temperature) -- This slide is a diagram illustrating how changes in temperature change erosion rates for processes involving glaciers, wind, mass movement and water (rivers and streams).  Cold conditions favor glaciers.  Both mass movement and water caused erosion increase with higher temperatures but water caused erosion predominates in hotter conditions. Wind is an active but minor agent at all temperatures   Adapted from Blumenstock & Thornthwaite, 1941

## Erosion Processes

**Notes:**
Erosion Processes (Precipitation) -- This slide is a diagram illustrating how changes in precipitation change erosion rates for processes involving wind, mass movement and water (rivers and streams).  Dry conditions favor wind.  Both mass movement and water caused erosion increase with added precipitation but water caused erosion predominates in wetter conditions.  Adapted from Blumenstock & Thornthwaite, 1941

## Mass Movements

**Notes:**
Mass Movements -- This slide depicts the extent of two mudflows that originated on Mt. Rainier and flowed northwest into the Puget Sound area.
The Osceola Mudflow occurred about 5000 years ago and the smaller Electron Mudflow occurred about 500 years ago.
Topinka, 1997, USGS

## Class Handout

**Notes:**
Class Handout --  This slide shows Rates of Geologic Processes for various categories including Deposition, Erosion, Sea Level, Crustal (Tectonic) and Crustal (Glacial).  The rates for the categories shown are listed in order of increasing rate that generally increase from 0.001 meters/1000 years to 100 meters/1000years. Copyright Geomax, P.C. used with permission.

## Slide Presentation Prepared ByGeomax, P.C.Dr. Donald R. Reichmuth, President1023 W. 30th Ave.Spokane, WA 99203-1324Phone & FAX – 509-838-6390E-mail – geomax@comcast.net

**Notes:**
This slide set for Session 3 was last edited on 12/15/04.