TM 3-34.61(TM 5-545/8 July 1971) GEOLOGY February 2013 Publication of TM 3-34.61, 12 February 2013 supersedes TM 5-545, Geology, 8 July 1971. This special conversion to the TM publishing medium/nomenclature has been accomplished to comply with TRADOC doctrine restructuring requirements. The title and content of TM 3-34.61 is identical to that of the superseded TM 5-545. This special conversion does not integrate any changes in Army doctrine since 8 July 1971 and does not alter the publication’s original references; therefore, some sources cited in this TM may no longer be current. For the status of official Department of the Army (DA) publications, consult DA Pam 25- 30, Consolidated Index of Army Publications and Blank Forms, at http://armypubs.army.mil/2530.html. DA Pam 25-30 is updated as new and revised publications, as well as changes to publications are published. For the content/availability of specific subject matter, contact the appropriate proponent. DISTRIBUTION RESTRICTION: Approved for public release; distribution is unlimited. HEADQUARTERS, DEPARTMENT OF THE ARMY This publication is available at Army Knowledge Online https://armypubs.us.army.mil/doctrine/index.html. TM 3-34.61 Technical Manual Headquarters No. 3-34.61 Department of the Army Washington, D.C., 12 February 2013 GEOLOGY Contents Page Chapter 1 INTRODUCTION ................................................................................................ 1-1 Purpose and Scope ............................................................................................ 1-1 Changes and Comments .................................................................................... 1-1 Definition of Geology .......................................................................................... 1-1 Geology and Military Operations ........................................................................ 1-1 Geology and Military Planning ............................................................................ 1-1 Chapter 2 MATERIALS OF THE EARTH'S CRUST .......................................................... 2-1 Section I - Minerals ........................................................................................... 2-1 Introduction ......................................................................................................... 2-1 Definition of a Mineral ......................................................................................... 2-1 Methods of Identification ..................................................................................... 2-1 Physical Properties of Minerals .......................................................................... 2-2 Rock-Forming Minerals ...................................................................................... 2-4 General Identification Characteristics ................................................................. 2-6 Section II - Rocks ............................................................................................ 2-11 Definition ........................................................................................................... 2-11 Major Rock Types ............................................................................................. 2-11 Igneous Rocks .................................................................................................. 2-11 Sedimentary Rocks .......................................................................................... 2-15 Metamorphic Rocks .......................................................................................... 2-20 Chapter 3 STRUCTURAL GEOLOGY ................................................................................ 3-1 Introduction ......................................................................................................... 3-1 Outcrops ............................................................................................................. 3-1 Attitude of Beds .................................................................................................. 3-1 Folds ................................................................................................................... 3-4 Faults ................................................................................................................ 3-10 Joints ................................................................................................................ 3-15 DISTRIBUTION RESTRICTION: Approved for public release; distribution is unlimited. *This publication supersedes TM 5-545, 8 July 1971. i Contents Chapter 4 WEATHERING AND EROSION ......................................................................... 4-1 Introduction ......................................................................................................... 4-1 Mechanical Weathering ...................................................................................... 4-1 Chemical Weathering .......................................................................................... 4-2 End Products of Weathering ............................................................................... 4-2 Depth of Watering ............................................................................................... 4-3 Erosion by Running Water .................................................................................. 4-3 Glaciation .......................................................................................................... 4-10 Wind Erosion ..................................................................................................... 4-14 Wave Erosion .................................................................................................... 4-14 Mass Movements .............................................................................................. 4-16 Chapter 5 VOLCANOES AND VOLCANISM ...................................................................... 5-1 Introduction ......................................................................................................... 5-1 Origin of Volcanoes ............................................................................................. 5-1 Types of Volcanic Cones .................................................................................... 5-1 Eruptive Volcanoes ............................................................................................. 5-2 Damage From Eruptions ..................................................................................... 5-3 Geographic Distribution of Volcanoes................................................................. 5-4 Fissure Flows ...................................................................................................... 5-6 Chapter 6 APPLICATIONS OF GEOLOGY TO ENGINEERING PROJECTS ................... 6-1 Introduction ......................................................................................................... 6-1 Dams ................................................................................................................... 6-1 Tunnels ............................................................................................................... 6-2 Roads and Airfields ............................................................................................. 6-3 Bridges ................................................................................................................ 6-3 Buildings .............................................................................................................. 6-4 Prospecting for Aggregate Materials ................................................................... 6-5 Quarry Operations ............................................................................................... 6-7 Chapter 7 GEOLOGY AND WATER SUPPLY ................................................................... 7-1 Introduction ......................................................................................................... 7-1 The Hydrologic Cycle .......................................................................................... 7-1 Surface Water as a Source of Water Supply ...................................................... 7-1 Streams ............................................................................................................... 7-3 Lakes ................................................................................................................... 7-4 Swamps .............................................................................................................. 7-4 Subsurface Water and its Occurrence ................................................................ 7-4 Porosity and Permeability ................................................................................... 7-5 The Water Table ................................................................................................. 7-7 Springs ................................................................................................................ 7-9 Artesian Water .................................................................................................. 7-10 Chapter 8 PHYSIOGRAPHY AND TERRAIN EVALUATION ............................................. 8-1 Basic Definitions .................................................................................................. 8-1 Plains and Plateaus ...........................................................................................