Cracks form for three reasons:

1) Exposed to more heat than needed for long periods of time:

During the firing process, Miriam’s Earthen Cookware withstands more than 2000 Degrees Fahrenheit, so it can certainly withstand high cooking temperatures. However, during cooking, the pot needs only a low heat setting to accomplish cooking your food (without damaging the nutritional cells), if the pot is let to cook on settings higher than medium, instead of indiscriminately throwing the heat onto the food, the pot will crack to form a vent for the heat to escape so it can maintain just the right amount of heat to complete the cooking process in this healthy manner.
Comparing this to cooking in metals and other materials: they need higher amounts of heat for cooking typically higher than medium settings. Many times a pot half or more full can only accomplish cooking at medium-high heat or more. Natural clay is an excellent retainer of heat and as a result, a lower stove setting accomplishes cooking just as well. On the other hand, conventional materials heat & cool at the same time so more heat is needed overall!

2) Long periods of uneven & sporadic heat:

If a pot is subject to uneven heat for long periods of time, one side of the bottom will heat up more than the other, causing the heated bottom portion to pull away from the cooler side.

In addition, high concentrations of thermal shock due to sporadic heating (like it happens with glass/ceramic cooktops) may damage the pot further. This is typically seen with glass/ceramic cooktops; as a result, we recommend using a heat diffuser on these cooktops. This will help distribute the heat more evenly to the pot.

3) Dry cooking:

Cooking high and dry is another cause. Cracks may form if the heat is too high, i.e. cooking above medium-low heat, especially when cooking dry or semi-dry recipes. It’s best to cook these kinds of recipes (like stir-fries and sautés) after the pot is fully seasoned. Additionally, heat settings should not be higher than medium-low heat on gas stoves or medium heat (at the most) on electric stoves with diffusers.
If you avoid cooking with high and uneven heat, you can have a pot that lasts forever! Please note that if your pot has a crack, the pot should not shatter. Cracks develop over time and it is still safe to use your pots despite these cracks, and if you go back to cooking at less heat, the crack should naturally heal (in this case, the crack will still be visible, but no leaking will come from it). For any cracks that continue to leak, here are two methods to help heal these cracks:

Any cracks that cause leaking can be healed by these two methods:

Method 1:
Thoroughly clean the pot with water and baking soda and wipe it dry with a cotton cloth. Set it aside to dry for about 5-10 minutes (if pot is already clean & dry, skip this step). Apply some oil (any cooking oil, like olive, coconut, or sesame seed) thoroughly with your hands onto the full surface of the pot (both inside and outside). Heat it in the oven at 250 degrees F for 25-30 minutes. Turn oven off; let pot cool down slightly before taking it out. After taking out of oven, let it sit for about 12 hours for the crack to fully heal. 
This process can also be done to strengthen the pot, if you ever experience chipping.

Method 2:
Make a paste with 2 tsp. water + 1 tsp. flour (any whole grain or other flour). Wash pot thoroughly and apply paste on outside and inside of pot along the crack line and a bit of the surrounding area. Let the paste dry slightly, then heat the pot with lid off on the stove on the lowest heat setting, until the rim is hot to the touch. When the pot is heated, clay platelets expand and come together and the paste will seal the crack. Wait for the pot to completely cool down before washing it.

You can repeat this process one more time if you still see liquids leaking from the crack, but in most cases, doing this one time should seal and heal the crack quite well.

After healing the crack using either method, you can additionally put 16″ or 14″; copper or steel wire (available at home improvement stores) under the rim of the pot, and twist the edges of the wire for it to stay in place (see image above).

It is important that the pot/pan gets to rest for 1-2 days after the healing process. When using for cooking after that please cook only on low to medium-low heat (medium heat maximum, if using on electric stove with diffuser). This process can heal cracks about 97% of the time.
Having tried this, if the pot continues to leak, here are ideas on other uses for this pot.