diff --git a/src/regolith/module_regolith.f90 b/src/regolith/module_regolith.f90
index 90e1e030..f3245e9e 100644
--- a/src/regolith/module_regolith.f90
+++ b/src/regolith/module_regolith.f90
@@ -117,7 +117,7 @@ subroutine regolith_subpixel_streamtube(user,surfi,deltar,ri,rip1,eradi,newlayer
       use module_globals 
       implicit none
       type(usertype),intent(in) :: user
-      type(surftype),intent(in) :: surfi
+      type(surftype),intent(inout) :: surfi
       real(DP),intent(in)       :: deltar,ri,rip1,eradi
       type(regodatatype),intent(inout)    :: newlayer
       real(DP),intent(inout)                :: meltinejecta,totvol
diff --git a/src/regolith/regolith_streamtube_head.f90 b/src/regolith/regolith_streamtube_head.f90
index 42984663..21240ca0 100644
--- a/src/regolith/regolith_streamtube_head.f90
+++ b/src/regolith/regolith_streamtube_head.f90
@@ -40,12 +40,13 @@ subroutine regolith_streamtube_head(user,surfi,deltar,totmare,tots,age_collector
                                                       ! head intersected with underlying layers, about 30% of volume difference. 
    real(DP) :: z,zstart,zend,zmin,zmax
    real(DP) :: tothead,totmarehead,marehead,vhead,vsgly
-   integer(I4B) :: N,M
+   integer(I4B) :: N,M,i
 
    ! melt collector
    real(DP) :: recyratio
    real(DP) :: headmeltvol
    real(DP) :: ratio
+   real(SP) :: limit
 
    !current => surfi%regolayer
    !current = surfi%regolayer
@@ -71,6 +72,14 @@ subroutine regolith_streamtube_head(user,surfi,deltar,totmare,tots,age_collector
       if (ratio > 1) then
          ratio = 1.0_DP
       end if
+      if (ratio > 0) then
+         limit = (TINY(1._SP) / ratio) * 2
+         do i=1,size(age_collector)
+            if(current(M)%age(i)<limit) then
+               current(M)%age(i) = 0
+            end if
+         end do
+      end if
       age_collector(:) = age_collector(:) + (current(M)%age(:) * ratio)
       headmeltvol = current(M)%meltvolume * ratio
       meltinejecta = meltinejecta + headmeltvol
@@ -90,6 +99,14 @@ subroutine regolith_streamtube_head(user,surfi,deltar,totmare,tots,age_collector
             if (ratio > 1) then
                ratio = 1.0_DP
             end if
+            if (ratio > 0) then
+               limit = (TINY(1._SP) / ratio) * 2
+               do i=1,size(age_collector)
+                  if(current(N)%age(i)<limit) then
+                     current(N)%age(i) = 0
+                  end if
+               end do
+            end if
             age_collector(:) = age_collector(:) + (current(N)%age(:) * ratio)
             headmeltvol = current(N)%meltvolume * ratio
             meltinejecta = meltinejecta + headmeltvol
@@ -108,6 +125,14 @@ subroutine regolith_streamtube_head(user,surfi,deltar,totmare,tots,age_collector
             if (ratio > 1) then
                ratio = 1.0_DP
             end if
+            if (ratio > 0) then
+               limit = (TINY(1._SP) / ratio) * 2
+               do i=1,size(age_collector)
+                  if(current(N)%age(i)<limit) then
+                     current(N)%age(i) = 0
+                  end if
+               end do
+            end if
             age_collector(:) = age_collector(:) + (current(N)%age(:) * ratio)
             headmeltvol = current(N)%meltvolume * ratio
             meltinejecta = meltinejecta + headmeltvol
diff --git a/src/regolith/regolith_streamtube_lineseg.f90 b/src/regolith/regolith_streamtube_lineseg.f90
index 05d6dda1..2c893e39 100644
--- a/src/regolith/regolith_streamtube_lineseg.f90
+++ b/src/regolith/regolith_streamtube_lineseg.f90
@@ -40,7 +40,8 @@ subroutine regolith_streamtube_lineseg(user,surfi,thetast,ri,rip1,zmin,zmax,erad
    type(regodatatype),dimension(:),allocatable :: current
    real(DP) :: z,zstart,zend,rstart,rend,r
    real(DP) :: vsgly,x,vseg, vsh
-   integer(I4B) :: N,M
+   integer(I4B) :: N,M,i
+   real(SP) :: limit
 
    ! Melt zone
    real(DP) :: recyratio, xsh, rst, ratio
@@ -88,6 +89,14 @@ subroutine regolith_streamtube_lineseg(user,surfi,thetast,ri,rip1,zmin,zmax,erad
                 if (ratio > 1) then
                   ratio = 1.0_DP
                 end if
+                if (ratio > 0) then
+                  limit = (TINY(1._SP) / ratio) * 2
+                  do i=1,size(age_collector)
+                     if(current(N-1)%age(i)<limit) then
+                        current(N-1)%age(i) = 0
+                     end if
+                  end do
+               end if
                 age_collector(:) = age_collector(:) + (current(N-1)%age(:) * ratio)
                 !vol              = vol + sum(current(N-1)%age(:)) * recyratio
                 linmelt = current(N-1)%meltvolume * ratio
@@ -132,6 +141,14 @@ subroutine regolith_streamtube_lineseg(user,surfi,thetast,ri,rip1,zmin,zmax,erad
                   vseg             = regolith_streamtube_volume_func(eradi,max(xmints,rstart),rend,deltar)
                   vsh              = regolith_shock_damage(eradi,deltar,xmints,xsfints,rstart,rend)
                   recyratio        = max((vseg-vsh),0.0_DP) / (user%pix**2) / current(N)%thickness
+                  if (ratio > 0) then
+                     limit = (TINY(1._SP) / ratio) * 2
+                     do i=1,size(age_collector)
+                        if(current(N)%age(i)<limit) then
+                           current(N)%age(i) = 0
+                        end if
+                     end do
+                  end if
                   age_collector(:) = age_collector(:) + current(N)%age(:) * ratio
                   ratio            = max((vseg-vsh),0.0_DP) / current(N)%totvolume
                   if (ratio > 1) then
@@ -153,6 +170,14 @@ subroutine regolith_streamtube_lineseg(user,surfi,thetast,ri,rip1,zmin,zmax,erad
                   if (ratio > 1) then
                      ratio = 1.0_DP
                   end if
+                  if (ratio > 0) then
+                     limit = (TINY(1._SP) / ratio) * 2
+                     do i=1,size(age_collector)
+                        if(current(N)%age(i)<limit) then
+                           current(N)%age(i) = 0
+                        end if
+                     end do
+                  end if
                   age_collector(:) = age_collector(:) + (current(N)%age(:) * ratio)
                   !vol              = vol + sum(current(N)%age(:)) * recyratio
                   linmelt = current(N)%meltvolume * ratio
@@ -182,6 +207,14 @@ subroutine regolith_streamtube_lineseg(user,surfi,thetast,ri,rip1,zmin,zmax,erad
                   if (ratio > 1) then
                      ratio = 1.0_DP
                   end if
+                  if (ratio > 0) then
+                     limit = (TINY(1._SP) / ratio) * 2
+                     do i=1,size(age_collector)
+                        if(current(N)%age(i)<limit) then
+                           current(N)%age(i) = 0
+                        end if
+                     end do
+                  end if
                   age_collector(:) = age_collector(:) + (current(N)%age(:) * ratio)
                   !vol              = vol + sum(current(N)%age(:)) * recyratio
                   linmelt = current(N)%meltvolume * ratio
@@ -201,6 +234,14 @@ subroutine regolith_streamtube_lineseg(user,surfi,thetast,ri,rip1,zmin,zmax,erad
                if (ratio > 1) then
                   ratio = 1.0_DP
                end if
+               if (ratio > 0) then
+                  limit = (TINY(1._SP) / ratio) * 2
+                  do i=1,size(age_collector)
+                     if(current(N)%age(i)<limit) then
+                        current(N)%age(i) = 0
+                     end if
+                  end do
+               end if
                age_collector(:) = age_collector(:) + (current(N)%age(:) * ratio)
                linmelt = current(N)%meltvolume * ratio
                meltinejecta = meltinejecta + linmelt
diff --git a/src/regolith/regolith_subpixel_streamtube.f90 b/src/regolith/regolith_subpixel_streamtube.f90
index f7ebe46b..acf2b08d 100644
--- a/src/regolith/regolith_subpixel_streamtube.f90
+++ b/src/regolith/regolith_subpixel_streamtube.f90
@@ -58,7 +58,7 @@ subroutine regolith_subpixel_streamtube(user,surfi,deltar,ri,rip1,eradi,newlayer
 
    ! Arguments
    type(usertype),intent(in) :: user
-   type(surftype),intent(in) :: surfi
+   type(surftype),intent(inout) :: surfi
    real(DP),intent(in)       :: deltar,ri,rip1,eradi
    type(regodatatype),intent(inout)    :: newlayer
    real(DP),intent(out)              :: meltinejecta, totvol
@@ -77,7 +77,8 @@ subroutine regolith_subpixel_streamtube(user,surfi,deltar,ri,rip1,eradi,newlayer
    !type(regolisttype),pointer :: current
    type(regodatatype),dimension(:),allocatable :: current
    real(DP) :: z,zmax,zstart,zend,rlefti,rleftf,rrighti,rrightf,rc,vsgly,vsgly1,vsgly2,x,mvl,mvr
-   integer(I4B) :: N,M
+   integer(I4B) :: N,M,i
+   real(SP)  :: limit, limit2
 
    ! Stream tube's distance from the edge of a melt zone 
    real(DP) :: zm, recyratio, xmints1, vseg, recyratio2, ratio, ratio2
@@ -108,6 +109,8 @@ subroutine regolith_subpixel_streamtube(user,surfi,deltar,ri,rip1,eradi,newlayer
    vsh2 = 0.0_DP
    ratio = 0.0_DP
    ratio2 = 0.0_DP
+   limit = 0.0_SP
+   limit2 = 0.0_SP
 
    ! Two cases: subpixel is inside the first layer, and its volume is simply the landing ejecta blanket.
    if (zend>=zmax) then 
@@ -124,6 +127,14 @@ subroutine regolith_subpixel_streamtube(user,surfi,deltar,ri,rip1,eradi,newlayer
          meltinejecta     = surfi%regolayer(M)%meltvolume * ratio
          distvol(:)       = distvol(:) + (surfi%regolayer(M)%distvol(:) * ratio)
          totvol           = vseg
+         if (ratio > 0) then
+            limit            = (TINY(1._SP) / ratio) * 2
+            do i=1,size(age_collector)
+               if(surfi%regolayer(M)%age(i)<limit) then
+                  surfi%regolayer(M)%age(i) = 0
+               end if
+            end do
+         end if
          age_collector(:) = age_collector(:) + (surfi%regolayer(M)%age(:) * ratio)
          !vol              = vol + sum(age_collector(:))
 !         write(*,*) '1',eradi, xmints, xsfints, &
@@ -224,6 +235,22 @@ subroutine regolith_subpixel_streamtube(user,surfi,deltar,ri,rip1,eradi,newlayer
          !distvol(:) = distvol(:) + (current(N)%meltdist(:)*(max((vsgly1-vsh),0.0_DP)+max((vsgly2-vsh2),0.0_DP)))
          if (ratio + ratio2 < 1.0_DP) then
             distvol(:) = distvol(:) + (current(N)%distvol(:)*(ratio)) + (current(N)%distvol(:)*(ratio2))
+            if (ratio2 > 0) then
+               limit2 = (TINY(1._SP) / ratio2) * 2
+               do i=1,size(age_collector)
+                  if(current(N)%age(i)<limit2) then
+                     current(N)%age(i) = 0
+                  end if
+               end do
+            end if
+            if (ratio > 0) then
+               limit = (TINY(1._SP) / ratio) * 2
+               do i=1,size(age_collector)
+                  if(current(N)%age(i)<limit) then
+                     current(N)%age(i) = 0
+                  end if
+               end do
+            end if
             age_collector(:) = age_collector(:) + (current(N)%age(:)*(ratio)) + (current(N)%age*(ratio2))
          else
             distvol(:) = distvol(:) + current(N)%distvol(:)
diff --git a/src/regolith/regolith_traverse_streamtube.f90 b/src/regolith/regolith_traverse_streamtube.f90
index abfd7096..06f60c44 100644
--- a/src/regolith/regolith_traverse_streamtube.f90
+++ b/src/regolith/regolith_traverse_streamtube.f90
@@ -41,7 +41,8 @@ subroutine regolith_traverse_streamtube(user,surfi,deltar,ri,rip1,eradi,erado,ne
    ! Traversing a linked list 
    real(DP) :: zri,zrip1,cosi,coso,rzmax
    real(DP) :: erad,z,zmin,zmax,thetast,vseg
-   integer(I4B) :: N
+   integer(I4B) :: N,i
+   real(SP) :: limit
 
    real(DP),parameter :: a = 0.936457
    real(DP),parameter :: b = 1.12368
@@ -95,6 +96,14 @@ subroutine regolith_traverse_streamtube(user,surfi,deltar,ri,rip1,eradi,erado,ne
          if (ratio > 1) then
             ratio = 1.0_DP
          end if
+         if (ratio > 0) then
+            limit = (TINY(1._SP) / ratio) * 2
+            do i=1,size(age_collector)
+               if(surfi%regolayer(N)%age(i)<limit) then
+                  surfi%regolayer(N)%age(i) = 0
+               end if
+            end do
+         end if
          age_collector(:) = age_collector(:) + (surfi%regolayer(N)%age(:) * ratio)
          meltinejecta     = meltinejecta + (surfi%regolayer(N)%meltvolume * ratio)
          distvol(:)       = distvol(:) + (surfi%regolayer(N)%distvol(:) * ratio)