Lecture Ground Ice Definition Classification Summary Ice content Genesis Form Process and Form Summary

Ground Ice Ground Ice Often found in permafrost Definition Ice Content Body of clear ice within frozen ground Ice Content Directly related to water content in a frozen conditions ICE CONTENT = Wt. of Ice/Wt. of dried soil x 100% Can’t usually go above porosity of the soil Can get very stupid results 95/5 x 100= 1900 % Moisture Content

Excess Ice Content Excess Ice Content Relates to ice rich samples Use volumetric measurements rather than weight measurements Put 100 g of sample in a beaker Water cannot fit into soil matrix (-supernatent water) H20 E.I.C.= 20% 100 cm3 * Upper limit to sample**

Important Storage Term: Gets Little Respect

Different Ways of Classifying Ground Ice 1) Genesis 2) Form 3) Examine Process and Form 1) Genesis: Ice in sediment While sediment is being laid down After sediment is being laid down

Continued If happening same time - SYNGENETIC ICE (does not happen very often-e.g. Siberia) If happening after a climatic change – EPIGENETIC ICE (e.g. Canada) Ground Ice - want to talk about excess ice content

> 2.5 cm < 2.5 cm N=Not Visible Vx= individual ice crystals or B= Bonded n= no excess ice e=excess ice F=friable, easy for it to fall apart (dry sand, little or no ice present) Vx= individual ice crystals or Inclusions Vs= stratified or distinctly oriented Ice formation (bands are right angle to heat flux) Vc=coatings on large particles in the soils VR= random, or irregularly formed ice formations

Process Form Classification-Mackay, 1972 10 different kinds of ice 1) Open Cavity ice Formed by sublimation of ice crystals directly from water vapour-crack -2 Deg. C Ground Surface -15 Deg. C -cooling of water vapour ….ice in crack due to sublimation

2) Single Vein Ice Penetration of water into an open fissure (liquid form)-re-freezing of a single vein within the ground. beginning of wedge ice

3) Repeated Vein Ice=Wedge Ice Cracking takes place repeatedly near vertical wedges Tends to crack repeatedly at the same place….see vertical foliation

Epigenetic Ice Wedges

Ice Wedge, NWT

4) Tension Crack Ice Pressure-sometimes by other features (e.g. pingos) 5) Closed Cavity Ice-RARE 6) Epigenetic Segregated Ice Movement toward a freezing plane Freezing Plane Movement of water from below to freezing plane

Continued Pore water migration Forms ice right behind the freezing plane Temps. –0.1 to –0.2 Deg. C Frozen fringe of soil Buildup of Ice Layer

Continued Freezing plane can remain stationary until we build up a thicker ice lense Ice lense-mm’s to 10’s of cm thick In course particles Freezing plane into coarse particles pushes water down and up Sands and gravels

Continued Pore Water Expulsion OCCURS-no where for the excess water to go-has to go into the unfrozen soil This is very important for pingo formation

Aggradational Ice Segregated Ice Ground Ice Slump ICE MUDFLOW

Continued Mudflow will dry up- 1 to 2 m deep Permafrost will grade into the bottom of it Porewater movement to the base of the mudflow Lenses of ice in the new permafrost -old mudflow -aggregated, segregated ice

8) Intrusive Sill Ice (Injection Ice) Water is injected into frozen soil f’table Injection of water, Gives rise to an Ice body p’table

Intrusive Pingo Ice Pingos are ice cored hills > 60 cm-up to 300 m in diameter Some cores are almost pure ice

10) Pore Ice Bonding ice which holds soil grains together Pore ice fill spaces, to get water, you must have coatings on particles Must have segregated ice to get water Pore Ice fills spaces

Proportions of Ground Ice Alaska North Slope-CREEL-Total vol: 1, 500 km3 71% of ground ice was pore ice Greatest conc. of ice near the top of the permafrost table. 50% Active Layer -below active layer, get wedge ice, therefore lots of ice

Continued Top portion of p’frost is rather warm Water vapour and liquid water can penetrate Year after year water trickles down ……..going to have an ice rich layer on top of the permafrost

Richard’s Island Pollard and French…. Upper 10 m over 2, 335 km2….vol: 10. 27 km3 *Pore ice most impt. *Pore ice and segregated ice-constitute over 80% of the total ice volume 20% other types were wedge ice 50% of the top m was excess ice

Massive Ice Does not contain much soil Very large exposure Largest in N. Siberia C. Yakuta….exposures are 70 m high N. America Beaufort Sea, Alaska, MacKenzie, 40 m thick Very large syngenetic ice wedges Epigenetic relies on cracking-can’t have thermal crack that high

Continued Could be buried Wisconsin Glacier Ice in the Mackenzie….suggested that it is buried glacier ice Ice at Peninsula Point Not glacier ice MacKay-bore hole data Logged for soil and ice 85% of cases-ice was underlain by sands or gravels Overlain was silts and clays Coast was below sea-emerged later ice

MASSIVE ICE BODY Movement of water to the freezing plane Clay and Silts Sand Sand Movement of water to the freezing plane Water going to build up lenses in the clay and silts MASSIVE ICE BODY

Ice Wedges Significant True indicators of permafrost 1 to 1.5 m in wide 3 to 4 m in depth 3 to 4 m wide 5 to 10 m deep DEEP FREEZING

Ice Wedge, NWT

Ice Wedges (continued) Favourable environment: Poorly drained tundra In the continuous p’frost zone Further north-arid-less snow Further south-hard rock, not severe enough **soils has to be cooled –15 to –20 Deg. C ** rate of cooling is also impt.

Gary Island Only 40% of ice wedges crack in any given year Wire to a recorder Records when Wire is broken Snow cover is a critical factor To see if cracks will open **Mackay put up snow fences and stopped cracking -max. growth after 6 years is 2 mm, < 1 mm/year

High Centred Ice Wedge Polygons, NWT Low Centred Ice Wedge Polygons, NWT

Eastwind Lake, Ellesmere Island (2005-2006) dry ground 10 20 m 1 -1 -2 -3 trough ice wedge active layer low-centred polygon after Mackay 1980 Hydrologic Connectivity of Tundra Ponds, Ellesmere Island, Nunavut By May Guan Seasonal Hydrochemistry of a Polar Oasis Wetland Complex By Dan Thompson Photo: K.L. Young

Pingo Two basic types Open System Pingo Occurs in the discontinuous permafrost zone, in areas that were not glaciated during the Wisconsin- Yukon, Alaska Tend to occur in valley bottom or valley slopes * can have circulation of groundwater….crucial in open system pingos

South North Piezometric WT Pingo Ice Permafrost Groundwater

Pingo Continued Pingo is below the top of the water table Need artesian pressures to start the pingos up Hydraulic head and ice segregation…these mound the pingo up Usually the substrate is sands and gravels…allows a permeability…may get a spring and a rupture.

Closed System Pingo Form In continuous permafrost…usually in low relief 2000-2500 pings-Mackenzie Delta Area has the highest concentration Pingos require a talik

LAKE P’FROST P’FROST TALIK

Pond sand Freezing Plane Water will move up To the freezing plane Pore water Expulsion as Freezing takes place

Pond is the thinnest layer, Build-up of pressures It will deform there Ice Pingo Hts. Pulsate -Change in hydraulic head -Hydraulic potential is changing…. -Impt. Component Unfrozen

IS OPEN/CLOSED DIVISION VALID?

Palsas 10- 50 wide 1 to 7 m Is a peat mound Peat overlies mineral soil Looks like peat plateaus They form in bogs and occur in the discontinuous zone 10- 50 wide 1 to 7 m Peat P’frost

Palsas Continued Snow-low…influences development Get deeper frost penetration Peat mounds are higher than surround zones Water movement is important-have ice formation in the higher areas More ice lense development raises the mound above the surrounding area….more snow blown off……CIRCULAR ARGUMENT Process tends to promote a higher mound

Continued Tend to be growing or dying…not in an equilibrium state

Ramifications

Summary Definition Classification Ice content Genesis Form Process and Form Pingos (open and closed)