Glacial Depositional Landforms

MICRO-REALM 01

Till vs. Outwash (NCERT)

GLACIAL TILL:
DIRECT ICE

OUTWASH:
MELTWATER

• Till: Unassorted coarse & fine debris
• Dropped directly by melting glaciers
• Outwash: Assorted & stratified by streams

MICRO-REALM 02

Angular Till Clasts

• Rock fragments in till are angular to
• Sub-angular in form (NCERT)
• Outwash pebbles are rounded at edges!

MICRO-REALM 03

Moraines Definition

• Long ridges of deposits of glacial till
• Named according to their position
• Relative to the valley glacier (NCERT)

MICRO-REALM 04

1. Terminal Moraines

TOE SNOUT →

• Long ridges of debris deposited at
• The end (toe/snout) of the glacier
• Marks maximum advance limit (NCERT)

MICRO-REALM 05

2. Lateral Moraines

∥ VALLEY WALLS ∥

• Form along the sides parallel to
• The glacial valleys (NCERT)
• Join terminal moraine in horse-shoe

MICRO-REALM 06

3. Medial Moraines

• Located in the centre of glacial valley
• Flanked by lateral moraines on sides
• Formed when two glaciers coalesce!

MICRO-REALM 07

4. Ground Moraines

• Valley glaciers retreat rapidly
• Leaves irregular sheet of thick/thin
• Till over valley floors (NCERT)

MICRO-REALM 08

Recessional & Push Moraines

• Recessional: Series of arcs from pauses
• During overall glacial retreat
• Push Moraine: Bulldozed by re-advance

MICRO-REALM 09

Drumlins Definition (NCERT)

• Smooth oval shaped ridge-like features
• Composed mainly of glacial till
• With some masses of gravel & sand

MICRO-REALM 10

Drumlin Dimensions (NCERT)

UP TO 1 KM LENGTH
× 30 M OR SO HEIGHT

• Long axes parallel to ice movement
• Measure up to 1 km in length
• And 30 m or so in height (NCERT)

MICRO-REALM 11

Stoss End vs. Tail (NCERT)

STOSS (BLUNT)
FACES ICE →→ TAIL
(TAPERING)

• One end facing the glacier = Stoss end
• Stoss is BLUNT & steeper than other end
• Other end = Gently tapering Tail!

MICRO-REALM 12

Subglacial Fissure Genesis

ICE STREAMLINING →

• Dumping of rock debris beneath heavily
• Loaded ice through fissures in glacier
• Stoss gets blunted by moving ice (NCERT)

MICRO-REALM 13

"Basket of Eggs" Topography

• Drumlins occur in swarms of thousands
• Inverted-spoon hills + marshy hollows
• Gives classic "Basket of Eggs" relief

MICRO-REALM 14

Drumlin vs. Roche Moutonnée

DRUMLIN:
TILL · STEEP STOSS

ROCHE MOUT.:
ROCK · STEEP LEE

• #1 UPSC Prelims ice-direction trap!
• Drumlin (Depositional Till): Steep Stoss
• Roche Moutonnée (Erosional Rock): Steep Lee

MICRO-REALM 15

Eskers (Sinuous Ridges)

• Very coarse materials like boulders & blocks
• Along with some minor rock debris
• Sinuous ridge after ice melts (NCERT)

MICRO-REALM 16

Subglacial Tunnel Genesis

• Summer meltwater flows beneath glacier
• Channel has banks of ice on either side
• Leaves sinuous embankment when ice melts

MICRO-REALM 17

Esker Embankment Highways

• Well-drained gravel ridge across bogs
• Used for roads & railways in Finland/Sweden
• And prime source of construction aggregate

MICRO-REALM 18

Outwash Plains (Sandur)

• At foot of glacial mountains or beyond
• Limits of continental ice sheets (NCERT)
• Broad flat coalescing glaciofluvial fans

MICRO-REALM 19

Valley Trains (Mountain)

• Outwash confined within U-shaped valley
• Braided meltwater gravel & sand floor
• Bhagirathi & Nubra valley trains

MICRO-REALM 20

Kettle Holes & Kettle Lakes

• Detached blocks of dead ice buried in outwash
• Ice block melts centuries later
• Leaves circular depression (Pitted Outwash)

MICRO-REALM 21

Kames & Kame Terraces

• Steep-sided mound of stratified sand/gravel
• Deposited in crevasses or against valley wall
• Forms Knob-and-Kettle hummocky terrain

MICRO-REALM 22

Glaciolacustrine Varves

• Annual sediment pair in proglacial lakes
• Summer: Light coarse silt (active melt)
• Winter: Dark fine organic clay (frozen lake)

MICRO-REALM 23

Lodgement vs. Ablation Till

ABLATION TILL (LOOSE)

LODGEMENT TILL (COMPACT)

• Lodgement Till: Plastered under heavy moving ice
• Ablation Till: Loose supraglacial debris
• Dropped as stagnant ice melts in place

MICRO-REALM 24

Kashmir Karewas (Zafran)

KAREWAS (KASHMIR VALLEY)GLACIAL CLAY + MORAINES

• Thick Pleistocene lacustrine + glacial clay
• Embedded with moraines on Pir Panjal flanks
• Famous for Zafran (Saffron) & Almonds!

MICRO-REALM 25

Talchir & Pokhran Tillites

PERMO-CARBONIFEROUS (~300 Ma)TALCHIR & BAP BOULDER BEDS

• Lithified ancient Gondwana glacial till
• Talchir Boulder Bed (Odisha/Damodar)
• Bap/Pokhran Boulder Bed (Rajasthan)

MICRO-REALM 26

Blaini Dropstones (Himalaya)

• Iceberg-rafted boulders dropped into sea mud
• Blaini Boulder Bed (Lesser Himalaya — ~635 Ma)
• Records Marinoan "Snowball Earth" glaciation

MICRO-REALM 27

Himalayan Moraine Dams

PROGLACIAL LAKE

• Terminal & lateral moraines dam meltwater
• Samudra Tapu (Chandra), Chorabari (Mandakini)
• Unstable unconsolidated till triggers GLOFs

MICRO-REALM 28

Master Glacial Drift Matrix

MORAINES (4)DRUMLINSESKERSOUTWASH

• Completes Glacial Geomorphology triad (53–55)
• Till (Moraines/Drumlins) vs Outwash (Eskers)
• Transitions to Realm 56 (Coastal Waves)