Is the frost line deeper if ground is saturated?

[Beltane]

We've had a TON of rain in these parts and my neighbor stated that the frost line will be much deeper this year when the ground freezes because of it. Is this true?

[tinknal]

Deepest frost I've ever seen was during a drought.

[primal1]

Dunno for sure about the frost line, but it is recommended to water the garden if you are expecting frost... so i hear.

[mpillow]

Water adds density to the soil so it takes longer to freeze and or go deeper BUT if we do get a long stretch of cold before a significant amount of snow....we are going to have some serious frost heaves in the Spring! (Think of it like a lake freezing/thawing)

My pond has flooded the pasture and the lawn....

[rambler]

Typically dry means the frost has a chance to go deeper.

Wet & it can take a while for it to thaw out in the spring (more cold mass) but it doesn't freeze nearly as deep.

--->Paul

[RedneckPete]

Frost is MUCH harder to dig through when the soil was wet. A backhoe can pop out a decent amount of frost if the soil is dry, but it is very difficult when the soil was wet.

Can't comment on the depth with relation to wetness, I've never really noticed a pattern. Typically the colder the winter, the deeper the frost.

Pete

[dcross]

Snow cover would have much more of an impact, I would think.

[Explorer]

Originally Posted by dcross

Snow cover would have much more of an impact, I would think.

Snow is an insulator of the soil. Wet soil forms ice near the surface and ice is also an insulator of what is below. Just as a lake freezes on the top, but the water down deeper stays a liquid.

[arabian knight]

Moisture in the soil a good soaking and snow cover will stop the frost from going down very far. No Snow Cover and little to no moisture the frost goes quite far.
A few years ago in my area we had very little snow far hardly ANY of the fall rains, after coming through a drought condition most of the summer~! and then January came around and when temps got to 20 below and lower Even Septic Systems were freezing~! The Septic Tank itself would be freezing over. Honey wagon people would come out Break the Ice Pump out and just HOPE that this would not freeze yet that year, And SOME even did then~!!!!

[DJ in WA]

Yes, wet soil is more dense, but that makes it a better conductor of cold, and so frost will go deeper. Think about it, insulation has fluff. Add water to it, and it loses it's ability to keep out cold. Snow has fluff, so is a good insulator.

Another way to increase soil density is with pressure, e.g. driving over it. One needs to bury water lines deeper over packed soil. Unpacked soil with fluff over it, like sod, leaves, etc, won't freeze as deep.

[Bearfootfarm]

Originally Posted by DJ in WA

Yes, wet soil is more dense, but that makes it a better conductor of cold, and so frost will go deeper. Think about it, insulation has fluff. Add water to it, and it loses it's ability to keep out cold. Snow has fluff, so is a good insulator.

Another way to increase soil density is with pressure, e.g. driving over it. One needs to bury water lines deeper over packed soil. Unpacked soil with fluff over it, like sod, leaves, etc, won't freeze as deep.

Nice theory except for one thing, "Cold" cant be conducted. Cold is the absense of heat. Heat is the energy that can be conducted. So if wet soil is a better conductor, then logic says the heat from the ground will be conducted more easily towards the surface. Also if its more compact it will transmit more of the suns heat into the soil.

[DJ in WA]

All right, I knew I'd bring out the physicists in the crowd, so we can figure this out.

Technically, you're correct, heat is conducted. But after heat is conducted away, what is left? Cold, or the absence of heat. So, the easier it is to conduct away heat, the quicker it will become cold.

True, compact soil will conduct heat from the sun better. But we're talking about winter here, a case where the atmosphere, even with sunshine, is colder than the soil. Soil temps and atmosphere temps will tend to equilibrate. In winter, soil will become colder (lose more heat than absorb), and the easier it is to lose the heat, the easier it will be to freeze.

Compact soil will be hotter in the summer and colder in the winter.

This is the reason I don't put on a wet coat in the winter - I don't want to lose heat quicker and have a colder body.

[rambler]

Ice forms pockets of air & becomes an insulator.

Wet ground will freeze more solidly, but the frost will not go as deep. You are wqrong on the wet deal.

You are correct, compacted soil will freeze deepr than fluffy soil. For one, less moisture can get into compacted soil to freeze into an insulation....

Side issues: Dry ground tends to crack & let the cold air get in deeper. Wet falls tend to have a lot more snow & insulate the ground.

Dry ground will freeze deeper. Wet ground will not let frost go as deep (ice insulates), but you will 'notice' the frost a lot more in spring, as all that water makes the top ground quite solidly frozen.

[Pouncer]

Here's another aspect to ponder:

Lack of snow cover (insulating quality) generally means deeper frost depth, regardless of moisture content of the soil itself. It's what is growing on top of it that matters.

Undisturbed treed areas typically have much shallower frost lines than either a grass lawn or dirt/gravel with no live cover at all.

Driving equipment and vehicles over the soil will definitely drive the frost deeper. Thus, an undisturbed area with no traffic may only have six inches or a foot frozen, yet an exposed area with little cover and vehicles may reach eight to ten feet in depth.

I know this is true from my work experience, but the evidence is plain to see to the eye, when you look over any swampy type area (in the summer) where snowmachines traveled regularly in the winter....you will see narrow strips of slower growth matching their tracks.

[Alice In TX/MO]

Move south. It won't matter.

[MarkNH]

It should make for a very interesting mud season if all this water in the ground is combined with a heavy snow pack over the winter. We've been lucky last few years with little mud as it's been dry going into winter.

The good part of all this wet ground is that's a little easier to do some stumping.

[DJ in WA]

“Wet ground will freeze more solidly, but the frost will not go as deep. You are wrong on the wet deal.”

As my wife will attest, I am rarely wrong, so I will explain.

“Ice forms pockets of air & becomes an insulator.”

In all my chemistry classes, I never heard of ice forming pockets of air. From what would it form them? Ice is less dense than water, but only because of hydrogen bonds which spread out the molecules.

Yes, ice can be an insulator, but at issue is whether it is a better insulator than dry ground. Good insulators have air pockets, or vacuums, with molecules spread out or absent so kinetic energy (heat) is harder to transfer from molecule to molecule.

Soil/ground has air pockets in it, especially if not compacted. When you pour water in it, the air pockets are obliterated with water. Then it is a worse insulator even when the water freezes. If ice was a better insulator than air pockets, one would do well to soak their coat and throw it in the freezer.

So wet ground freezes deeper for the same reason as more compact ground – fewer air pockets.

IMHO

[Macybaby]

Well, my husband has done dirt work for years (MN, WI, SD) and he will say that wet soil will be harder, but the frost is not as deep as dry soil. He worked at a school for 7 years, so each January they were digging up the same area - the "Playground" where they taught adults how to operate heavy equipment.

Wet soil will cause way more problems with heaving and cracking of cement, or busting pipes, so having a lot of water around/under slabs before it freezes can really cause problems. Since water expands when it freezes, wet soil will move a lot more than dry soil. That heaving may be way more a concern than the depth of the frost line.

We had a lot of problems at our last place if we had a lot of rain right before it got cold. Last year we had a lot of problems with rain and freezing, but that was becuase the water froze on top of everything before it had a chance to soak in. Major ice storm the day after thanksgiving - that is no fun!

Cathy