getting a PC error and an unaligned address in store error when storing word

so, I have a MIPS program trying to sort an array of ints by selection sorting. I'm attempting to test it before I print it back out, (so right after the ints are supposed to be stored back into the array) I get "Exception occurred at PC=0x004000e8" and then "Unaligned address in store: 0x00000001" and then the program crashes. If anyone would like to help me understand why, that would be awesome! My program so far is:

the largest amount of nums in the array can be 256, hence the .space 1024 .data prompt1: .asciiz "enter number of elements in the array "

prompt2:     .asciiz "enter array elements, one per line:\n"

newline:     .asciiz "\n"

        .align 2
list:   .space 1024

        #i is $s0
        #n is $s1
        #address of list will be in $s2
        #minpos will be in $s3
        #j will be in $s4
        #temp will be $t5
        .text
main:   la $s2, list

        #promt the user for array size
        la $a0, prompt1
        li $v0, 4
        syscall

        #read int from console for n
        li $v0, 5
        syscall
        move $s1, $v0

        #prompt for elements
        la $a0, prompt2
        li $v0, 4
        syscall

        li $s0, 0
        #loop $s1 times
for:    #i<n:branch on i>=n
        bge $s0, $s1, for_exit

        sll $t0, $s0, 2
        addu $t0, $t0, $s2

        li $v0, 5
        syscall

        sw $v0, 0($t0)

        addi $s0, $s0, 1

        j for

for_exit:
        li $s0, 0
        #put n-1 in $t0
        move $t0, $s1
        addi $t0, $t0, -1





        #find correct element
        #i<n-1: branch on $s0 >= $t0
for2:
        bge $s0, $t0, for_exit2
        #look for correct element
        move $s3, $s0 #minpos = i
        addi $s4, $s0, 1 #j = i+1

        #j<n: branch if $s4, >= $s1
innerfor:
        bge $s4, $s1, innerfor_exit

        #time to get list[j] andd list[min_pos]
        move $t1, $s3 #t1 = minpos
        move $t2, $s4 #t2 = j
        sll $t1, $t1, 2 #minpos*2
        sll $t2, $t2, 2 #j *2
        add $t1, $t1, $s2 #(minpos*2) + array address
        add $t2, $t2, $s2 #(j*2) + array address
        lw $t8, 0($t1) #t1 = list[minpos]
        lw $t9, 0($t2) #t2 = list[j]

        #if(list[j] < list[minpos])
        #branch if list[j] >= list[minpos]

if:
        bge $t9, $t8, if_exit
        move $s3, $s4

if_exit:
        addi $s4, $s4, 1 #j++
        j innerfor

innerfor_exit:
        #t5(temp)gets list[i]
        move $t4, $s0 #t4 = i
        sll $t4, $t4, 2 #4i
        add $t4, $t4, $s2 #t4 = list[i]
        lw $t5, 0($t4) #temp = list[i]

        sw $t8, 0($t4) #list[i] = list[minpos]
        sw $t5, 0($t8) #list[minpos] = temp (= orig list[i])
        addi $s0, $s0, 1
        j for2

for_exit2:
        la $a0, newline
        li $v0, 4
        syscall

        li $s0, 0
        #for i<n: branch if $s0>= $s1

I know I get a little wild with temps down near the bottom, but that's just because I was starting to stress. Thanks in advance!