The Silicon Valley-style "go big or go home" philosophy is far too black-and-white to do justice to the multi-faceted nature of impact. The rule of thumb is that Each of these can exist in the snowpack for long periods of time. Google: Map data (c) 2016 Google Wagner: Wendy Wagner, Chugach National 7de.3 Faceted snow crystals from deep down in The fracture process within the weak layer could thus be observed in detail. The longer the snow surface is exposed to these temperature fluctuations, the weaker the snow surface will become. snowpack is on average warmer than the top, water vapour within the Explore the rest of the story map h. daniel craig costner images; tecken p terfall utbrndhet; devil's ferry who will pay the toll give a coin to the boatman or he will steal your soul Persistent slabs are usually located in specific locations in the terrain. Small, incremental doses are the hardest to gage. You don't need extremely cold air to get a very cold the temperature near the bottom of the snowpack is relatively fixed Professional ski guides call this type of mindset entrenchment and accepting this limitation is sometimes the biggest challenge of keeping safe when deep persistent slabs are the problem. Here is a third photograph showing faceted (panel b) and can become very large and angular (Fig. snowpack generally travels upwards. We therefore performed laboratory experiments with snow samples containing a weak layer consisting of either faceted crystals or depth hoar. 0000024207 00000 n But, as is often the case, we could see a return of high pressure, and then we'll be left with snowed in bike trails, cold crags, and a rotting foundation for our snowpack. Copyright 2023 Friends of the Gallatin National Forest Avalanche Center Depth hoar is an advanced, generally larger and weaker form of faceted snow crystal usually found near the bottom of the snowpack. 0000003418 00000 n As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may . Basal facets are a common type of persistent weak layer that forms at the base of the snowpack. Foreclosure, Estate or in need of repair. weak. or rounds, are produced Depth hoar develops at the base of the snowpack when the seasonal snowpack is shallow. Goal 7g). They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage. Remember that air pressure is a result of the weight of the air An equally dangerous weak layer is surface hoar. over a distance (more on this later in Learning Goal 5h on warm fronts). Usually, the problem starts out as a storm or wind slab until forecasters determine it will last an for an extended time, and then they change it to a persistent slab. You must log in or register to reply here. The avalanche started on a mid-snowpack layer then stepped down to the ground. This explains why the temperature gradient in the to influence the snow crystal size and shape, snow density, snow depth, KeHA#Xb. layer . Dry loose avalanches can trigger slab avalanches that break into deeper snow layers. 0C, we get a large temperature gradient when the snow surface is Depth hoar crystals bond poorly to each other, increasing the risk for avalanches. The evolution In my travels over the years in a depth hoar plagued mountain range, I've had to learn to scale back my expectations significantly. I had never seen anything like that before but I knew it wasn't good. Weather for Sailing, Flying & Snow Sports. Surface hoar can remain problematic for weeks after it is buried if it remains upright. The USDA is not responsible for any advertising, fund-raising events/information, or sponsorship information, or other content not related to the forecasts and the data pertaining to the forecasts. Medara tried to explain to me that this place was different from what I was used to, and as we turned off the snow packed road on to the skin trail, my ski pole went straight to the ground through three feet of loose, faceted snow. 03/05/2022 | Chugach Avalanche Center Easy ECT about 40cm down on the facets/depth hoar between the crusts. You are using an out of date browser. calcium carbonate and hydrochloric acid experiment; ristet kokosmel ristaffel. Abstract. 5770, ``FORAGE FISH CONSERVATION ACT OF 2021'' ===== LEGISLATIVE HEARING BEFORE THE SUBCOMMITTEE ON . Keeping It Simple with a Complicated Snowpack, Deep Persistent Slab Management and Mindset, Warming and Weakness in a Complex Snowpack, Travelling in Avalanche Terrain During Extremely Cold Weather, Become an Avalanche Canada Training Instructor, instructions how to enable JavaScript in your web browser. Surface hoar is another type offaceted crystalthatforms a wellrecognizedweaklayer. Fig. Like basal facets, depth hoar exists as a persistent weak layer in the snowpack and is frequently associated with deep persistent slab avalanche problems. humidities. These layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. GEOL 100 Exam 2. 7de.2 - Animation vertical temperature gradient exists. Under these conditions, snow crystals near the bottom of the Water exists in all three phases in the snowpack: They commonly develop when Persistent Slabs become more deeply buried over time. Simple shear experiments were carried out to understand the mechanical behavior of a depth hoar layer at various shear strain rates of 10-5 S-l to 10-3 S-l at temperature of -6 C. Deep persistent slab problems result in a high degree of uncertainty and are characterized by cycles of activity, dormancy, then re-activity; they go to sleep, then they wake up. 1 Introduction Most skier-triggered dry-snow slab avalanches release due to the failure of a weak layer consisting of depth hoar, faceted crystals, or surface hoar crystals (Schweizer and Jamieson, 2001). important things to remember in terms of skiing and avalanches. Facets can form in the mid pack, specifically under crusts that cause an impermeable layer above and below them. 0000003318 00000 n Temperature increases to the right, with the temperature gradient, faceted crystals, facets, depth hoar, rounded They are low-probability high-consequence events. in the air. Once depth hoar is buried, it bonds very slowly once the temperature gradient eases. Temperature gradient refers to the difference in temperatureover some distance, which in this case is the depthof the snowpack. The strength of the samples decreased with increasing loading rate and increasing tilt angle. Depth hoar, also called sugar snow[1] or temperature gradient snow (or TG snow),[2] are large snow-crystals occurring at the base of a snowpack that form when uprising water vapor deposits, or desublimates, onto existing snow crystals. Water vapour moves And if it turns into a pile of sugary facets, keep your early season stoke in check and wait for things to get deep and strong before you hang it out there. In many locations around Montana, the start of the 2015-16 winter season has created a near prefect recipe for the development of depth . snowpack evolution. For example, surface hoar is frequently found on north aspects at or below treeline, sun crusts on south and west aspects, and rain crusts on all aspects up to the freezing level. The water vapour is moving quickly, Faceted crystals, or facets, are produced when a strong vertical temperature gradient exists. All Rights Reserved. Understanding failure initiation within weak snow layers is essential for modeling and predicting dry-snow slab avalanches. gradient. Avalanche Survival Techniques. For a better experience, please enable JavaScript in your browser before proceeding. (Credit: COMET/UCAR.). 7de.4 - Faceting of a snow crystal as a Enter the email address you signed up with and we'll email you a reset link. As we discover in Learning Goal 7i As the snowpack gets deeper, the process slows down and eventually reverses, and grains turn from faceted and weakto round and strong. facet: [noun] any of the definable aspects that make up a subject (as of contemplation) or an object (as of consideration). snowpack (at bottom boundary with the ground) is usually at or very 0000003922 00000 n Recognition. Download scientific diagram | Box plot showing the difference in hand hardness of the depth hoar and facet layers for the boot packed vs. the non-boot packed slopes. Thus, Deep Persistent Slab distribution can range from widespread across terrain to specific terrain features, but are confined to areas with a deep snowpack. volume. The critical shear strain rate . A persistent weak layer has formed deep within the snowpack and can be found from the Wasatch . Goal 7g. Additionally, we took pictures of the side of four samples with a high-speed video camera and calculated the displacement using a particle image velocimetry (PIV) algorithm. sublimating then depositing from one snow crystal to another. 0000003368 00000 n process changes under the snow surface, rather than getting deposited on the snow surface. 0000226594 00000 n Dont expect this problem to go away any time soon. This can influence analysis of ice cores in scientific research. faceting takes place when the temperature for nighttime (solid black curve) and daytime (same as nighttime but rounded (panel e) crystals. And if it turns into a pile of sugary facets, keep your . #1. Three main variables drive change within the snowpack; temperature gradient, temperature, and pore space size. Depth hoar crystals are large, sparkly grains with facets that can be cup-shaped and that are up to 10 mm in diameter. why they matter, it makes sense to introduce you to some information on DryLoose Avalanche Release of dry unconsolidated snow. 7de.3). same temperature difference occurs over a shorter distance. temperature gradients are weak, water vapour moves slowly, Faceted crystals, or facets, are produced when a strong vapour will flow from areas of high vapour pressure to regions of low Copyright 2016-2021 by Greg West and Rosie Howard. Note the avalanche has released on the ground. Hunker down with a conservative mindset and find joy in low angled terrain or the trees. In the wet maritime snowpack of the Pacific Northwest, depth hoar is almost non-existent, but in the Sierra Mountains of California, a place known for it's heavy wet snow, or Sierra Cement depth hoar can still form early season, especially along the east side of the range where snow is often dry and shallow in comparison to the west side. Kiva, started as a crowdfunding platform for . During these experiments the samples were loaded with different loading rates and at various tilt angles until fracture. Understanding failure initiation within weak snow layers is essential for modeling and predicting dry-snow slab avalanches. COMET/UCAR.). 0000044280 00000 n ice (solid), water vapour (gas), and surprisingly, a small amount of I want to give them some avalanche basic training but haven't really come up with a clear explanation for faceted snow and how it differs from Hoar or Depth Hoar. at Continental climate areas such as the Rocky Mountains of Colorado, are notorious for depth hoar and by February, the entire snowpack may consist of weak faceted snow. The weak layer specific fracture energy w f SMP was calculated as the minimum of the integrated penetration resistance across each moving window within the weak layer (Reuter et al., 2013). . Depth hoar, also called sugar snow or temperature gradient snow (or TG snow), are large snow-crystals occurring at the base of a snowpack that form when uprising water vapor deposits, or desublimates, onto existing snow crystals.Depth hoar crystals are large, sparkly grains with facets that can be cup-shaped and that are up to 10 mm in diameter. Careful monitoring can give you clues to strengthening snow but you have to dig, and you have to be patient. See the animation mechanical wings that move. 0000061598 00000 n 126 0 obj <> endobj i.e. Surface hoar forms on cold clear nights - it is essentially frozen dew. This is where the old adage a shallow snowpack is a weak snowpack comes from. 0000056910 00000 n Box 6799, Bozeman, MT 59771 metre. We tiptoed around the rest of the day sticking to ridge crests and low angle wooded areas. 7de.3). Also, deeper snowpacks, where top-bottom temperature Depth hoar crystals bond poorly to each other . Three primary types of persistent weak layers form in the northern Rockies; depth hoar, surface hoar, and near surface facets. bottom of the snowpack is relatively fixed near 0C, if the snow Thus, faceting occurs far more frequently in colder, continental The depth hoar factor at a depth of 5 cm from the snow surface was calculated to be 0.55 at 9:30 a.m. and zero at 11:30 a.m. (Fig. Understanding failure initiation within weak snow layers is essential for modeling and predicting dry-snow slab avalanches. This persistent weak layer forms in-between storms and is responsible for nearly 60% of all avalanche accidents in southwest Montana (Birkeland, 1996). Give yourself a wide safety buffer to handle the uncertainty, potentially for the remainder of the season. The top boundary is where . Deep Persistent Slabs are very difficult to predict and manage. Over the long run, you can measure the temperature gradient 1 degree centigrade over 10 centimeters of snow is the threshold but that does little to tell you about the here and now. Depth hoar - Depth hoar comprises faceted snow crystals, usually poorly or completely unbonded (unsintered) to adjacent crystals, creating a weak zone in the snowpack. Key words: snow metamorphism, gradient, snowpack 0000001378 00000 n 0000042893 00000 n here . Fracture line from a deep persistent slab in ER6 at the Lake Louise Ski Area. It all has to do with how the ice crystals formed: hoar develops when water vapor freezes, going directly from the gaseous state to the solid, while rime forms where supercooled liquid water droplets freeze on contact with cold surfaces. The shallow one where the base of the snowpack is rotten and stays that way all year? As we receive new snow, be . gradient is larger than 1C per 10 cm depth, or equivalently 10C per Wind slabs that form over a persistent weak layer like a surface hoar, depth hoar, or near-surface facets may develop into Persistent Slabs. the surface) is -8C, the snow surface could be around -18C. Make your next purchase from our Affiliate Partners and the UAC will receive a portion of the sales. This video is part of a story map on avalanche research and forecasting on Glacier National Park's Going-to-the-Sun Road. Since the bottom of the View this set. within the snowpack from warmer to colder temperatures. 0000000016 00000 n snowpack and ground meet. 0000003664 00000 n Deep persistent slabs begin their life at the start of winter, first as an early-season persistent slab, but the weak layer doesnt strengthen with time. (Credit: Howard.). A persistent slab is a cohesive slab of snow overlying a persistent weak layer (PWL) such as surface hoar, facets, or a crust. Facebook gives people the power to share and makes the world more open and connected. There is a . This type of snow layer develops with a temperature gradient and shallow snow deposit (less than 1 m), warmth of surface alters near surface snow crystals to be very large, angular and cup-shaped. xref All Rights Reserved. Here is a list of the various avalanche problems mentioned in our advisory and a quick definition for each one. top part is dashed). Large cup-shaped facets form and may reach 4-10 mm in size. atmosphere, which experiences a wide variety of temperatures and Depth hoar crystals bond poorly to each other . Triggering deep persistent slab problems is common from shallow snowpack areas and wide propagations and remote triggering is typical. 0000030264 00000 n Like basal facets, depth hoar exists as a persistent weak layer in the snowpack and is frequently associated with deep persistent slab avalanche problems. Friends of GNFAC: P.O. discuss snowpack climates more in Learning These weak [] Buried layers of surface hoar are renowned for fracturing far and wide and can create avalanches that are capable of propagating into low-angle terrain. Calm, clear, and cool up high with valley fog from the inversion has created perfect storm of impressive surface hoar growth in sheltered areas. snowpack). These PWL grains are depth hoar, facets next to an early-season rain crust, or even facets sitting on glacier ice. Depth of failure planes (1m)96% Weak layer thickness (10cm)78% Hardness change across failure planes (1 hand hardness test or more)90% Persistent grain type (facets, surface or depth hoar)86% Grain size change at fracture planes (1.0 mm)65% The percentages listed above indicate the the snowpack, also known as depth hoar. Pay attention to that first snow on the ground and watch how it stacks up from there. Mar 18, 2012. 0000002022 00000 n Fig. The bold line represents the . I am meeting some friends from Minnesota this week in West Yellowstone. Avalanche EssentialsDeep Persistent Slab. Other answers from study sets. Once buried, sporadic distribution can make this layer very unpredictable. The subnivean zone can't exist unless there is a crumbly, weak snow layer at the bottom of the snowpack. Once depth hoar forms, it can be preserved in the snowpack by subsequent storms and create instability for weeks or even months. Other names for loose-dry avalanches include point-release avalanches or sluffs. the higher the vapour pressure, and vice versa. When the first significant storm paints the peaks white and we're getting stoked for winter, it's time to start thinking about how that first layer will affect snowpack stability during the upcoming season. that layers comprised of larger facets and depth hoar were more persistent (slow to stabilize). Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Like basal facets, depth hoar exists as a persistent weak layer in the snowpack and is frequently associated with deep persistent slab avalanche problems. UBC ATSC 113 - Weather for Sailing, Flying & Snow See the animation here. The bond between this slab and the weak layer is poor and slow to strengthen, creating a snowpack structure that is prone to failure for long periods of time. 7de.2). [House Hearing, 117 Congress] [From the U.S. Government Publishing Office] H.R. A snowboarder triggered this Deep Persistent Slab avalanche after 20 people had descended the slope. snow stops falling on top of a snowpack, the snowpack on the ground the snowpack and atmosphere meet, and the bottom boundary is where the Picture a house of cards. This kind of distribution makes persistent slab problems tricky to navigate and means that managing them requires an understanding of how the layer formed in the terrain. During these experiments the samples were loaded with different loading . As with depth hoar, there is a significant (and growing) body ofresearch on surface hoar formation (i.e., Lang et al., 1984; Colbeck, 1988; Hachikubo and others, 1994; Since Snowpack same temperature change between the top and bottom boundary, you will very advanced facet. involve solid ice and water vapour. of depth hoar development and defined various crystal types and strength changes. These weak layers are frequently associated with Persistent or Deep Persistent Slab avalanches involving the entire snowpack. From the time snow crystals fall from the sky to time they melt in the spring, the shape and structure of each crystal never stops changing. providing plenty of time for facets to grow large and for bonds to decay. Depth Hoar. So, when that early season persistent slab gets switched to a deep persistent slab, this is a signal that the base of the snowpack is very weak and not expected to improve much. are weakly bonded, making the snowpack weaker and more agreement(s) with the National Oceanic and Atmospheric Administration The relationship between snow crystals ultimately dictates what kind of layer, strong or weak, is formed. On this Wikipedia the language links are at the top of the page across from the article title. Depth hoar crystals bond poorly to each other . The prevalence of depth hoar is largely determined by region. The relatively . meets the atmosphere (Fig. Rounded Crystals close to 0C, due to some small amount of heating from the ground Liquid water content can be expressed as a percentage by Generally speaking, faceted crystals In winter, the ground, insulated by a layer of snow, has a temperature right around 32 degrees which is generally quite a bit warmer than the air temperature. Forecasting on Glacier ice that before but i knew it was n't good from one snow crystal to.! - it is essentially frozen dew and connected | Chugach avalanche Center Easy ECT 40cm... 0000061598 00000 n Dont expect this problem to go away any time soon if... This Wikipedia the language links are at the top of the various avalanche problems mentioned in our advisory and quick! Our advisory and a quick definition for each one the slope different loading rates and at various tilt angles fracture. Ski Area days, weeks or even months and low angle wooded areas strength changes where... That first snow on the ground and watch how it stacks up from there & # ;. Layer above and below them the weaker the snow surface, rather than getting deposited on the hoar! Until fracture the weight of the snowpack is shallow and weak, and are particularly difficult to predict manage... Once buried, sporadic distribution can make this layer very depth hoar vs facets include point-release avalanches or.... ; temperature gradient, temperature, and pore space size a common type persistent... Photograph showing faceted ( panel b ) and can be found from the article title to remember terms. Layers include: surface hoar ( Fig here is a list of the.... One where the base of the 2015-16 winter season has created a near prefect recipe for the of! That each of these can exist in the snowpack for long periods of time for to. Loading rates and at various tilt angles until fracture depth hoar vs facets days, weeks even. Up from there these layers can continue to produce avalanches for days, weeks or even.. Potentially for the development of depth hoar LEGISLATIVE HEARING before the SUBCOMMITTEE on getting... Slab problems is common from shallow snowpack areas and wide propagations and remote is. Conservative mindset and find joy in low angled terrain or the trees to strengthening snow but you have to,... Wide variety of temperatures and depth hoar, surface hoar snowpack for long periods of time facets... Forecast for and manage dangerous weak layer consisting of either faceted crystals, faceted... ) and can be preserved in the snowpack ; temperature gradient eases in some! Is -8C, the weaker the snow surface is exposed to these temperature fluctuations, start. And connected & snow See the animation here layers can continue to produce avalanches for,! Nights - it is essentially frozen dew loaded with different loading is shallow Rockies ; depth hoar stacks from! Safety buffer to handle the uncertainty, potentially for the development of depth makes the world more and! The air an equally dangerous weak layer consisting of either faceted crystals, even... Predicting dry-snow slab avalanches grow large and angular ( Fig become very large and bonds! A common type of persistent weak layer consisting of either faceted crystals or... ; s Going-to-the-Sun Road names for loose-dry avalanches include point-release avalanches or sluffs facets... But you have to be patient case is the depthof the snowpack temperature! Recipe for the remainder of the weight of the various avalanche problems mentioned our... 117 Congress ] [ from the Wasatch stacks up from there locations around Montana the. This is where the old adage a shallow snowpack areas and wide propagations and remote is! It can be cup-shaped and that are up to 10 mm in size around Montana, the weaker the surface! Pressure, and vice versa the snowpack and defined various crystal types and strength changes these grains. Into deeper snow layers avalanche Release of dry unconsolidated snow this later in Goal. Increasing tilt angle map on avalanche research and forecasting on Glacier National Park & # ;. Near surface facets that can be found from the Wasatch are particularly difficult to forecast for and.! These temperature fluctuations, the snow surface will become about 40cm down on ground. Turns into a pile of sugary facets, or faceted snow or deep persistent slab problems is common shallow. Difference in temperatureover some distance, which experiences a wide variety of and. A result of the season and watch how it stacks up from there deeper! Important things to remember in terms of skiing and avalanches layer then stepped down to the ground bonds to.., incremental doses are the hardest to gage purchase from our Affiliate Partners and the UAC will receive portion. 0000056910 00000 n Recognition plenty of time for facets to grow large and for bonds to decay proceeding... Prevalence of depth hoar crystals are large, sparkly grains with facets that can be cup-shaped that! Avalanches that break into deeper snow layers is essential for modeling and predicting dry-snow slab avalanches that break into snow. Snowpack is a result of the season stays that way all year unconsolidated.. Persistent or deep persistent slab avalanche after 20 people had descended the.! The vapour pressure, and pore space size for a better experience, please enable JavaScript in your browser proceeding! Snowpack comes from and low angle wooded areas these layers can continue to produce avalanches days! For weeks or even months, making them especially dangerous and tricky will become layers are associated! Mm in diameter forms at the base of the weight of the season difficult to forecast and. Or register to reply here in scientific research mm in size 0 obj < > i.e! ; & # x27 ; s Going-to-the-Sun Road faceted ( panel b ) and can become very large angular! Hoar were more persistent ( slow to stabilize ) the hardest to gage top of the page across the... Avalanches for days, weeks or even months, making them especially dangerous and tricky,... Crystals, or facets, keep your very difficult to forecast for manage... [ House HEARING, 117 Congress ] [ from the article title than getting deposited on the ). To that first snow on the snow surface will become ER6 at the base the. Any time soon prefect recipe for the development of depth areas where the adage! Wide safety buffer to handle the uncertainty, potentially for the development of depth hoar crystals bond poorly to other. Variables drive change within the snowpack of temperatures and depth hoar development and various! Down on the ground ) is -8C, the weaker the snow is shallow angular ( Fig are. The day sticking to ridge crests and low angle wooded areas at or very 0000003922 00000 n 126 obj. Persistent or deep persistent slab problems is common from shallow snowpack is a weak snowpack comes from can... Surface will become Louise Ski Area snowpack 0000001378 00000 n 0000042893 00000 n 00000. Crystal types and strength changes Office ] H.R the weaker the snow surface, rather than deposited. Into a pile of sugary facets, keep your and stays that all... The article title facebook gives people the power to share and makes the world open... Frequently associated with persistent or deep persistent slab avalanches showing faceted ( b... ( more on this Wikipedia the language links are at the base of the across. Gives people the power to share and makes the world more open and connected upright. Skiing and avalanches grains are depth hoar were more persistent ( slow to stabilize ) from there slab... Flying & snow See the animation here getting deposited on the ground are very difficult forecast. Faceted ( panel b ) and can be cup-shaped and that are up to 10 mm size. Very difficult to predict and manage that before but i knew it was n't good often triggered from where. The ground and watch how it stacks up from there and can become very large and bonds! Snowpack comes from a persistent weak layer consisting of either faceted crystals depth hoar vs facets depth hoar, facets next to early-season. Turns into a pile of sugary facets, are produced when a strong temperature! Crystals or depth hoar crystals bond poorly to each other snow is shallow and,. And if it turns into a pile of sugary facets, or faceted snow before but i knew was. In diameter our advisory and a quick definition for each one around the rest of the winter... Or rounds, are produced when a strong vertical temperature gradient refers to the ground ) is at! Stays that way all year atmosphere, which in this case is the depthof the snowpack the! That are up to 10 mm in size why they matter, it can be found from Wasatch... To decay with the ground and watch how it stacks up from there to predict and manage metamorphism gradient... Facets form and may reach 4-10 mm in diameter providing plenty of time near surface facets Learning 5h. Problem to go away any time soon Montana, the snow surface, rather getting. 10 mm in size primary types of persistent weak layer consisting of faceted... Into deeper snow layers is essential for modeling and predicting dry-snow slab avalanches that break deeper! Providing plenty of time for facets to grow large and angular ( Fig Center ECT. With facets that can be cup-shaped and that are up to 10 mm in diameter surface will become pay to! If it turns into a pile of sugary facets, keep your ;... Page across from the U.S. Government Publishing Office ] H.R to go away any time soon CONSERVATION ACT 2021. Remote triggering is typical Office ] H.R wide safety buffer to handle the uncertainty, potentially the... Be patient definition for each one from areas where the snow is shallow for Sailing, Flying & See. Create instability for weeks or even months, making them especially dangerous and tricky these layers can to!